These two nice examples of the 10-ponder Parrott rifle are in terrific shape: their limbers, carriages, barrels and all other things weaponry are in terrific condition. I know as of a few years ago these two cannons were restored. These rifles are more rarer than the 3-inch ordnance rifles and the Napoleons which seems to be everywhere. The Parrot is very similar to the 3-inch ordnance save for the band around the breech which makes it distinguish it self from the 3-inch ordnance. Also, the Parrott has a flare at the end of the muzzle and the 3-inch does not. 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 particular rifle has a cylindrical piece of wood jammed down its bore rendering it useless.
The two rifles and the Battery B, 1st New Jersey - US Battery Marker are located on the left or west part of Hancock Avenue if traveling north toward the 
Pennsylvania Monument which looms hugely in the distance. The 10-Pounder Parrott rifles, no. 247 is to the left and no. 244 is to the right. Both cannons were manufactured at the West Point Foundry. Both cannons point to to the west. The New York State Auxiliary Monument is directly across the road. This part of the battlefield is the south section of Cemetery Ridge. 
Parking is available at small, cutout shoulders along the road, some wide, some narrow. Be sure to stay off the grass or you will be ticketed by park police. I visited this monument on Thursday, July 5, 2012 at 5:45 P.M. I was at an elevation of 601 feet, ASL. I used a Canon PowerShot 14.1 Megapixel, SX210 IS digital camera for the photos.
The 1st New Jersey Artillery (Battery B) served a a member of Randolph's Brigade in Third Corps, Army of the Potomac. The unit was commanded by Captain Adoniram J. Clark (1838-1913), who was a medical student in Newark. In his post-war life, he was Chief of Police for Newark , New Jersey. Under his command, the 1st brought 143 men and 6 Parrott rifles to the field of battle and among the men, 1 was killed, 16 were wounded and 3 went missing.
My SOURCE for all things weapons at Gettysburg provided me additional information about this weapon which did not appear on the muzzle. I used red to designate that data. The rest is as it appears exactly on the muzzle, starting at the top or just to the left of the 12 o'clock position and moving clockwise.
No. 247 ......1863 ......W.P.F. ......2.9 ......A.M. ......925 ......GRVS 3RH ...... FDY #105
No. 247 refers to the Army registration number, a way for the military to keep track of the guns when the received a shipment from the various foundries which supported the Union efforts. 1863 refers to the date of manufacture. W.P.F. refers to the foundry, West Point Foundry out of Cold Spring, NY. The foundry is on the National Register of Historic Places. 2.9 is designation of the rifle and refers to the size of the bore in inches. The 10-Pounder designation in the name refers to weight of the projectile which was more like 9.5 pounds. These weapons go by both names. A.M. are the initials of the inspector who gave the gun a once over before it was shipped out to the Federal army. The initials stand for Alfred Mordecai. 925 refers to the weight of the firing tube, usually a kind of a fingerprint for these things as each one is unique to the rifle. GRVS 3RH, information provided by my source, refers to number of rifling grooves, left or right twist. In this case, 3 right hand twists were made to rifle this cannon. If you were to look at the close-ups of the muzzle stamps, the rifling grooves are easy to discern. Finally, FDY #105 is an internal control number specific to the foundry.
About the Foundry
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 Parott'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 Inspector
Alfred Mordecai (June 30, 1840 - January 20, 1920) graduated from West Point in 1861 and fought for the Union. His father of the same name was an ordnance officer of great fame and finding information on him was a snap From the West Point/Cullums Register SITE I learned: Mordecai was a cadet at the Military Academy from July 1, 1857, to June 24, 1861, when he was graduated and promoted in the Army to Brevet Second Lieut., Top. Engineers, June 24, 1861. Throughout his career he served constantly in varying ordnance capacities, eventually as an instructor.
Colonel Mordecai became the Superintendent and Commandant of the Springfield Armory from 1892 to 1895. He retired from active service on January 20, 1904 at his own request, after 40 years' service as a Brigadier-General. He resided in Washington D.C. and died on January 20, 1920 in Washington D.C. at the ripe old age of 80, having lived to see World War I. He is buried in Oak Hill Cemetery, Washington, DC.
About the Gun
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
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.
The most common rifled field artillery piece in Civil War service generally, the 10-pdr. Parrott was made of cast iron with wrought iron breech reenforcement. It was an accurate and reliable weapon. Confederate versions of the Parrott Rifles were built by the Noble Brothers Foundry and the Macon Arsenal in Georgia. This Parrott design went through several improvements during the war and was changed in 1863 to a larger 3-inch bore and matching Parrott shell. By 1864 the 3-inch Parrott was standardized and most of these 2.9-inch guns were withdrawn from service.
One of the pages of the Historical Marker Database also provided some interesting 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.
The tablet marks the position and actions of the Battery B, 1st New Jersey Artillery on July 2, 1863 reads as follows:
Army of the Potomac
Third Corps
Artillery Brigade
New Jersey Light Artillery
2nd Battery
Six 10 pounder Parrotts
Captain A. Judson Clark Commanding
July 2 Engaged in the action in a field near the Peach Orchard retired to the rear about 6.30 p.m. for want of support.
July 3 In line here with the Artillery Brigade during the heavy cannonading and the charge and repulse of Longstreet's Assault but was not engaged.
Casualties July 2nd Killed 1 man. Wounded 16 men. Missing 3 men. Total 20.