What a sight for the Lincoln Highway! There are four 3-inch ordinance guns displayed at the four corners of the pedestal of the Buford statue along Route 30. The cannons surrounding the monument are the actual pieces of Calef's Battery, 2nd United States Artillery, Battery A. According to a a small bronze plate attached to the top of barrel, the gun facing down Chambersburg Pike was the opening gun of the battle, firing the first Union artillery shot of the battle under General Buford's personal direction. Captain Calef tracked it down after the war using its serial number, 223. This waymark is for that specific gun. All of the guns are detached from their carriages and are lain across blocks of granite. The guns are slightly inset up to their trunnions into the granite blocks which were carved out to support each gun. If facing the statue with your back to the highway, and from the front-right gun moving to the rear or counterclockwise, the guns are numbered with the following registry information (the one in green is the first shot cannon):
1. No. 632 ......PICo ......1863 ......816 lbs ......J.H.V.F.
2. No. 244 ......PICo ......1862 ......816 lbs ......T.T.S.L.
3. No. 756 ......PICo ......1864 ......816 lbs ......S.C.L.
4. No. 233 ......PICo ......1862 ......816 lbs ......T.T.S.L. ......[First Gun Fired]
The bronze plate reads:
The four cannon guarding the base of the statue
belonged to
Horse Battery "A" 2nd U.S. Artillery
This piece was
the opening gun of the battle
fired from this spot
under the personal direction of Gen. Buford.
July First, 1863.
There is great dispute over who fired the first shot; many people claim that honor. I wonder if it is really such an honor given the catastrophic consequences of that great Battle. Down the road, 1.79 miles west of this position at coordinates N 39° 51.057 W 77° 16.843 is another First Shot marker. Being there is a fancy bronze marker attached to a cannon, I say this is the site of the first cannon shot. Who knows, maybe there is a distinction between the first rifle shot and the first cannon shot and the information here is indeed accurate.
These cannons are much smaller than the other Confederate cannons used here in 1863. The tubes are black, very smooth, in terrific shape and represented at the time, some pretty serious weapon technology. This is an 1861 model but was manufactured in 1862 and may or may not have seen action at Gettysburg. This model was also mass-produced by the Confederates, once they got their hands on a Federal version. The stamp on this muzzle as well as the other three guns are pristine which is where I was able to find the information presented above. This waymark is for the front gun to the left of the monument, pointing down the Lincoln Highway.
The four 3-inch guns and the Buford Monument are northwest of Gettysburg and are located on Route 30, The Lincoln Highway, on the right or north side of the road if traveling north northwest. Stone-Meredith Avenue is directly across the street. Diagonally across the street is a guide station with maps, rest rooms, water and an office to ask questions. There are 13 parking spaces here as well as three more spots across the street on Stone Avenue at an extended shoulder. These guns are supposed to represent the armaments used by this battery during the Battle of Gettysburg. 
I visited this monument on Thursday, July 5, 2012 at 9:46 AM & at an elevation of 579 feet, ASL.
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, 12 o'clock position and moving clockwise.
No. 233 ......PICo ......1862 ......816 lbs ......T.T.S.L. ......FDY #244......GRVS 7RH
No 233 refers to the Army registration number, a way for the military to keep track of the guns when it took receipt of each weapon. PICo refers to the Phoenix Iron Company in Phoenixville, PA, the foundry where the fun was manufactured (More on that below). 1862 refers to the production date. T.T.S.L. 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 the very famous Union Army Inspector, Major Theodore Thadeaus Sobibski Laidley. 816 refers to the weight of the firing tube. This number is on the bottom of the muzzle. Each gun is usually very unique and has its own weight which distinguishes it from every other gun, like a fingerprint. For some reason, there are a whole bunch of these guns with the same weight. I am unsure how that is even possible given the lack of precise manufacturing technology foundry's had in 1862. The weight of this gun is significantly lighter (about 300 pounds) than some of the Confederate Napoleons used during the Battle of Gettysburg. FDY #244 is an internal control number specific to the foundry. The carriages were approximately 900 pounds which makes this entire weapon approximately 1,700 pounds or so. The GRVS 7RH, more information provided by my source, refers to number of rifling grooves, left or right twist. In this case, 7 right hand twists were made to rifle this cannon, a feature which is discernible from the muzzle photos I took.
About the Foundry
The Phoenix Iron Works (1855: Phoenix Iron Company; 1949: Phoenix Iron & Steel Company; 1955: Phoenix Steel Corporation), located in Phoenixville, Pennsylvania, was a significant manufacturer of iron and related products during the 19th century and early 20th century. Phoenix Iron Company was a major producer of cannons for the Union Army during the American Civil War. The company also produced the Phoenix column, a significant advance in construction material. Phoenix Iron Works is a core component of the Phoenixville Historic District, a National Register of Historic Places site and in 2006 was recognized as a Historic Landmark by ASM International. SOURCE & SOURCE
About the Inspector
Theodore Thaddeus Sobieski Laidley (1822 - 1886) was an army officer specializing in ordnance. He was also an inventor and author. Laidley was born in Guyandotte, Virginia April 14, 1822. He graduated in 1842 from the U.S. Military Academy and chose a commission in the ordnance corps and served in the Mexican War. At the end of the war, he returned to the arsenal at Watervliet, New York, as Assistant Ordnance officer. Laidley was put on detached service to write a new ordnance manual published in 1862 which served as an important guide during the Civil War. He served on several ordnance boards designing and testing weapons, taking out eight patents. He was later president of the commission to test the strength and value of all kinds of iron, steel, and other metals at the Watertown, Mass. arsenal 1871-1881, retiring in 1882. Laidley wrote government reports and A Course of Instruction in Rifle Firing, Philadelphia, 1879. Theodore Laidley died in Palotka, Florida April 4, 1886. He was inducted into the Ordnance Hall of Fame in 2008. SOURCE, SOURCE, & SOURCE
About the Gun
The second most common rifled field artillery in both Armies generally, and the most common on the Maryland Campaign, the 3 inch Ordnance gun was made of hammer-welded, formed, machined iron. It was popular because of its accuracy and reliability, at least those examples built in Federal shops. Less precise machining and lower-grade iron gave their Confederate counterparts more trouble. Those built by the firm of Burton and Archer were know to be problematic. The 3-inch rifle normally fired Hotchkiss or Schenkel shells that weighed between 8 and 9 pounds. In an emergency it could use 10-pounder Parrot ammunition. It could also be used to fire cannister but, as a rifle, was not as effective with this as howitzers or Napoleons. The maximum range of this weapon was 1830 yards, with the barrel/tube Length 69 inches, the bore 3 inches (hence the name) and the total combined weight (already mentioned above), approximately 1720 pounds. Johnson, Curt & Anderson, Richard C., Artillery Hell: Employment of Artillery at Antietam, College Station, TX: Texas A&M University Press, 1995; and
Schwartz, Peter, Artillery at Gettysburg online. SOURCE & SOURCE.
The Major General John Buford Statue is a contributing feature to the Gettysburg National Military Park Historic District which is nationally significant under NR Criteria A, B, C & D. Areas of Significance: Military, Politics/Government, Landscape Architecture, Conservation, Archeology-Historic. Period of Significance: 1863-1938. The original National Register Nomination was approved by the Keeper March 19, 1975. An update to this nomination was approved by the Keeper on January 23, 2004. The statue is catalogued as structure number MN030-D.
From the nomination form:
Marks spot where Buford stood on a.m. of July 1, 1863 & ordered Calef to open fire with his battery. Located on McPherson Farm between Chambersburg Pike & RR line. Incorps 4 cannons of Calef's battery & base, including tube that fired opening shot.
Short Physical Description:
Mn & 4 cannons. Statue, 9' high on rough hewn pedestal, 3'6" sq, 4'6" high. Base 5'sq 2' thick. Inscription on S of base. Bronze inscription tablets on N & S of pedistal. At 4 corners 3' ordinace rifle tubes mounted on slabs.
Long Physical Description:
Bronze statue that is surrounded by four cannons. Statue of Buford is set on a rough hewn granite pedestal that rests on a five foot square base. A rifle tube is mounted on each of four three-foot high granite piers at each of the four corners of the pedestal and bronze inscription tablets are located on the north and south faces of the pedestal. One of the tubes fired the opening Union shot of the battle on July 1, 1863 as part of Buford’s command. An inscription is found on the south side of the base. Overall height is 15.6 foot. Sculptured by James E. Kelley. Located on the McPherson farm on the north side of the Chambersburg Pike.
This site is the very best the Lincoln Highway has to offer at Gettysburg. This area is loaded with all types of cannons and guns, a veritable outside museum. I would suggest allowing up to forty-five minutes to fully inspect all the tablets, monuments and weapons in this area.