This replica (probably) is a decent example of a 10-pounder Parrott and naturally, is in terrific shape: its limber, carriage, barrels and all other things weaponry are in terrific condition. Some of those components look to be authentic. I know that on or before June 28, 2008 this rifle was not present at this site. These rifles are more rare than the 3-inch ordnance rifles and the Napoleons which seems to be everywhere; perhaps this is why this may have been fabricated post-production to account for a shortage of these weapons to display on the battlefield.
The Parrot is very similar to the 3-inch ordnance save for the band around the breech which makes it distinguish itself from the 3-inch ordnance. A replicated example of the 3-inch ordnance flanks the other side of this tablet. Also, some Parrotts have a flare at the end of the muzzle (eliminated in 1863) and the 3-inch does not. The muzzle of this one is straight as an arrow. Another similarity the two rifles share is the deep incised stamp that runs along the outer muzzle which make identification very easy and accurate; this one is devoid of those marks.
I sometimes notice writing on both of the cannon's trunnions. The proper right trunnion is stamped R.P.P. R.P.P. are the initials of Captain Robert Parker Parrott, the inventor of the Parrott Rifle. The proper left trunnion is stamped 10 PDR which of course refers to the weight of the projectile ordnance. The gun tubes made by Parrott's foundry are identifiable by the letters WPF (West Point Foundry) found on the gun tube, along with the initials RPP for Robert P. Parrott. I have also found stamped at the top of the breech information about the bore which simply reads: 3. IN. BORE.. The bore was not enlarged to a 3-inch size until 1863 so that bit of information at least acts as an identifier. Not curiously however, this Parrott rifle does not have any identifying marks on it. As a result, this guns is expectedly anonymous as I could not recover the registry or foundry numbers.
The manufacturing of the gun carriages is an interesting story. After the war, Calvin Gilbert conducted a foundry @ Gettysburg and manufactured metal gun carriages to replace the rotted wooden ones. He also cast the battery tablet at this site as well as the other ones about the battlefield. Gilbert joined the 87th Pennsylvania Volunteers when the "Rebellion" broke out. Since he was musically inclined, he was made a member of the regimental band. In early 1863, he was promoted to the rank of Captain and sent to Washington D.C. for commissary duty. He served in that capacity until the war ended in 1865, and at war’s end earned the brevet rank of Major. 
After returning home to Gettysburg, Major Gilbert moved his family to the town of Chambersburg, where he served as the Superintendent of Schools. He also opened an iron foundry there in 1868. When Calvin learned, nearly thirty years later, in 1894, that the Gettysburg Foundry was available, he purchased it with a business partner & moved his family back to Gettysburg. For the next twenty years, the Calvin Gilbert Foundry created ironworks that are still seen today on many historic forts and national battlefields (this tablet), from upstate New York to Florida to Lookout Mountain. Gilbert lived to be 100 years old and attended the Last Reunion of the Blue and Gray for the 75th anniversary of the Battle of Gettysburg when he was 99. He was a most remarkable man who lived an amazing life.
There is an excellent excerpt in the American Guide Series about Gilbert attending the 75th reunion anniversary.
The rifle and the 
Raine's Lee Artillery Battery tablet are located @ the very end of Benner's Loop, at the cul-de-sac. Wrap around the circle and start heading north, back to the main road, Hanover Road. The rifle is on the right side of the road or at the 9 o'clock position on the circle if pointing north toward Hanover Road. Parking is available all up and down the narrow road and especially at the cul-de-sac. If facing the tablet, to the right is a replica 10-pounder Parrott rifle and to the right, a replica 3-inch ordnance rifle. Take care to not park on anything remotely green as Park Police will happily ticket you. I visited this site on Monday, July 1, 2013 on the 150th anniversary of the Battle of Gettysburg @ 1:12 PM, EDT. As always, I used my trusty and oft abused Canon PowerShot 14.1 Megapixel, SX210 IS digital camera for the photos.
About the Foundry
As far as I know, these Parrott rifles were made exclusively @ the West Point Foundry in 1863. Although this weapon probably was not produced at W.P., we can still take time to learn about the original supplier. The West Point Foundry was an early ironworks in Cold Spring, New York that operated from 1817 to 1911. Set up to remedy deficiencies in national armaments production after the War of 1812, it became most famous for its production of Parrott rifles and other munitions during the Civil War, although it also manufactured a variety of iron products for civilian use. The rise of steel making and declining demand for cast iron after the Civil War caused it to gradually sink into bankruptcy and cease operations in the early 20th Century.
In 1835, Captain Robert Parker Parrott, a West Point graduate, was appointed inspector of ordnance from the foundry. The next year, he resigned his commission and on October 31, 1836 was appointed superintendent of the foundry. It prospered under his tenure, and was the site of numerous experiments with artillery and projectiles, culminating in his invention of the Parrott rifle in 1860. During Parrott’s tenure, in 1843, the foundry also manufactured USS Spencer, a revenue cutter which was the first iron ship built in the U.S. The foundry's operations peaked during the Civil War due to military orders: it had a workforce of 1,400 people and produced 2,000 cannon and three million shells. Parrott also invented an incendiary shell which was used in an 8-inch Parrott rifle (the "Swamp Angel") to bombard Charleston. The importance of the foundry to the war effort can be measured by the fact that President Abraham Lincoln visited and inspected it in June 1862.
SOURCE
About the Gun
The most common rifled field artillery piece in Civil War service was the 10-pdr. Parrott . The gun was invented by Robert Parker Parrott, a West Point graduate. He resigned from the service in 1836 and became the superintendent of the West Point Foundry in Cold Spring, New York. He created the first Parrott Rifle (and corresponding projectile) in 1860 and patented it in 1861. SOURCE This Parrott design went through several improvements during the war. The U.S. M1863 10-pounder Parrott was slightly modified from the M1861 pattern; the bore was increased to 3.0 inches in 1863 with a matching Parrott shell, to make its ammunition consistent with that of the new 3-inch ordnance rifle, and the muzzle swell was eliminated. By 1864 the 3-inch Parrott was standardized and most of these 2.9-inch guns were withdrawn from service. Parrotts were manufactured with a combination of cast iron and wrought iron. The cast iron made for an accurate gun, but was brittle enough to suffer fractures. On the Parrott, a large wrought iron reinforcing band was overlaid on the breach. Although accurate, the Parrott had a poor reputation for safety and they were shunned by many artillerists.
I also remembered the Antietam Battlefield people placed a small identification marker sticking out of the ground next to one of their Parrotts which read:
10-POUNDER PARROT RIFLE
The cast iron rifle with its band of wrought iron reinforcing
the breech was a modern weapon of the day. It was effective at
moderately long range. The 20-pounder, similar except for size,
was the heaviest rifled cannon used at Antietam.
Confederate versions of the Parrott Rifles were built by the Noble Brothers Foundry, the Macon Arsenal in Georgia and Tredegar Iron Works, Richmond, VA. Confederate cast Parrott rifles used seven hook-slant or "Brooke" type rifle grooves, and can be identified by the taper on the trunnion side of the reinforcing band.
One of the pages of the Historical Marker Database also provided some interesting and corroborating facts about this weapon and history about the rifle: This 3-inch Parrott Rifle was produced at West Point Foundry in 1864, well after the battle. At the battle, the Parrott Rifles on the field were actually 2.9-inch bore models, commonly called 10-pounder Parrotts. Problems arose with logistical support, since similar shells were made for the 3-inch Ordnance Rifles. The Army opted to replace all 2.9-inch weapons with the slightly larger bore, and West Point began producing "new" Parrott rifles with 3-inch bores.
About the Battery
The Lee Artillery Battery served as a member of Latimer's Battalion, Johnson's Division - Ewell's 2nd Corps. The Battery was commanded by Charles I. Raine. who was killed by a solid shot at Mine Run, Virginia, serving with Andrews Battalion on November 29, 1863.
Lee Light Artillery was organized at Lynchburg, Virginia, in May, 1861. This unit was active in Lee's Cheat Mountain Campaign and Jackson's Valley operations, then served in J.W. Latimer's, R.S. Andrews', and C.M. Braxton's Battalion of Artillery, Army of Northern Virginia. It fought with the army from the Seven Days' Battles to Cold Harbor, then participated in Early's Shenandoah Valley Campaign. The battery took 90 men to Gettysburg and surrendered at Appomattox with 12. It was under the command of Captains Pierce B. Anderson, William W. Hardwicke, and Charles I. Raine. SOURCE
The tablet marks the position and actions of Raine’s Lee Artillery Battery on July 2-4, 1863. The principal reason for the tablet's placement at this position were for the events on July 2 when this Battery engaged Union forces at Culp's Hill. Culp's Hill (N 39° 49.206 W 77° 13.220) is .54 miles southwest or 219° from this position. SOURCE The marker reads as follows:
Army of Northern Virginia
Ewell's Corps - Johnson's Division
Latimer's Battalion - Raine's Battery
The Lee Battery
Two 20 pounder Parrotts - one 10 pounder Parrott
and one 3 inch Rifle
July 2 The 10 pounder Parrott and 3 inch Rifle took position here about 4 p.m. and were engaged in the severe cannonade that lasted over two hours. They also aided in supporting the attack of Johnson's Infantry on Culp's Hill and did not retired to the rear until dark. The 20 pounder Parrotts took an active part in the cannonade from their position some distance in the rear of the other guns.
July 3 The 20 pounder Parrotts were actively engaged in the great cannonade
July 4 Withdrew from the field with the Battalion.
Losses - Wounded 8 - Horses killed 3
The rifles (incorrectly called cannons) are also identified in the NRHP nomination and narrative form. The pertinent information is highlighted with red font.
From the Nomination Form:
Civil War tablet that marks position of Raine's Lee CS Battery, known as "The Lee Artillery", July 2-4, 1863. Narrates events associated with the Battery during Battle of Gettysburg.
Short Physical Description:
Tablet w/ 2 cannon. Cast iron tablet, 3'8" x 3'4", with raised inscription painted in a contrasting color and mounted on fluted cast iron post. All 4'4" H. Cannon located left & right of tablet. Tablet cast by Calvin Gilbert, founder.
Long Physical Description:
Located at Benner's Hill, west side of avenue at road end.
My Sources
1. NRHP Nomination Form
2. Stone Sentinels
3. Virtual Gettysburg
4. Draw the Sword