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. The carriages are also equally pristine. This is an 1861 model but was manufactured in 1864. Naturally, this cannon was never fired at Gettysburg as it was produced after the Battle. This model was also mass-produced by the Confederates as well. I found it to be rather interesting that this gun is supposed to represent the Confederate weaponry deployed at this position, yet it is a Federal gun, inspected by a Federal officer. So much for authenticity at Gettysburg. In fairness, it must be difficult to locate these guns in the 21st century so I am sure they are doing the best they can. Thankfully, both gun muzzles still have well-defined stamps, which list all the manufacturing information (more on that below).
The two guns/cannons and monument are across from Schultz woods and to the right or south of the National Guard Armory, on West Confederate Avenue, on the left or east side when traveling south; the guns face the east, in the direction of the Federal lines as they were in July of 1863. This area is Seminary Ridge and is near the Lutheran Theological Seminary. 
Parking is rather easy in this area as there are extra wide shoulders. Stay off the grass. There are many monuments and cannons in this area so expect to be here for at least 30 minutes or more to see everything. The guns were recently removed for maintenance and replaced in the last 4 or 5 years (the carriages were empty as of August 16, 2008). I visited the two guns and monument on Saturday, March 10, 2012 at approximately 11:41 PM, just before the clocks were set ahead for the Spring. I was at 559 feet ASL elevation.
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 and moving clockwise:
No 784 - PICo - 1864 - 816 lbs. - S.C.L. - FDY #843 - GRVS 7RH .
No 784 refers to the Army registration number, a way for the military to keep track of the guns. PICo refers to the Phoenix Iron Company in Phoenixville, PA, the foundry where the fun was manufactured. I believe when the Rebels were able to capture one of these guns, they copied it and produced their own, although this one was federally made. 1864 refers to the date of manufacture (1864) even though this is an 1861 model. 816 lbs 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 1864. S.C.L. are the initials of the inspector who gave the gun a once over before it was shipped out to the army. S C L are the initials of Stephen Carr Lyford, an ordinance inspector for the federal government who approved this and the other gun/cannon after it was made. FDY #843 is information not found on the muzzle but provided by the website. This is an internal control number specific to the foundry. The carriages were approximately 900 pounds which makes this entire weapon over 1,700 pounds. 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.
About the Inspector
Born on August 15, 1838 in New Hampshire, Lyford graduted from West Point on June 24, 1861 and served with distinction as a Lieutenant Colonel throughout the Civil War. He died on May 9, 1885 while on active duty in command of the Rockford Arsenal, Pennsylvania. He is buried in Section 1, Site 9 at Arlington National Cemetery.
SOURCE I also found this biography: Stephen Carr Lyford (New Hampshire) was commander of the Cairo, Illinois, ordnance depot from February to May, 1862, and chief of ordnance in the Department of Tennessee from July 11, 1862, to September 6, 1863. Lyford returned to West Point as assistant professor of mathematics (1865-1867) and as instructor of ordnance and gunnery (1872). In 1874, he went to Japan, where he presented the emperor with arms and books. At the 1876 International Exhibition in Philadelphia, Lyford was a judge for sporting arms, weapons, and explosives. He died at the Frankford, Pennsylvania, arsenal, which he commanded, in 1885. SOURCE
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 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 tablet, which marks the position of Maurin's CS Battery on July 2-4, 1863 and narrates those events reads as follows:
Army of Northern Virginia
Hill's Corps Heth's Division
Garnett's Battalion Maurin's Battery
The Donaldsville Artillery
One 10 pounder Parrott, Two 3 inch Rifles
July 1 About 3.30 p.m. relieved some of Pegram's guns whose ammunition was exhausted on the ridge west of Herr's Tavern and from that time to an active part in the conflict.
July 2 In position here all day but not actively engaged until 3 p.m. when it opened and maintained a steady fire on Cemetery Hill until near sunset and vigorously renewed it at dusk for the purpose of diverting the fire of Union artillery from the Confederate infantry then assaulting East Cemetery Hill.
July 3 Ordered to a position south of McMillan's Woods and held in reserve sometimes fired upon but not returning the fire.
July 4 Withdrew about 8 a.m. and marched to Cashtown to reinforce the cavalry escorting the wagon train.
Losses not reported in detail.
This area is loaded with all types of cannons and guns, a veritable outside museum. I would suggest allowing up to an hour to fully inspect all the tablets, monuments and weapons in this area.
Other Sources
1.
Find a Grave
2.
Civil War Artillery
3.
Arlington National Cemetery Website