The 6th Corps, 1st Division, 3rd Brigade was also known as Russell’s Brigade. During the battle of Gettysburg, it served as a member of Wright’s Division in the Sixth Corps, Army of the Potomac. The brigade was commanded by Brigadier General David Allen Russell (December 10, 1820 – September 19, 1864), a career United States Army officer who served in the Mexican-American War and the American Civil War. He was killed in action as a brigadier general in the Union Army. In 1864, Russell fought in the Overland Campaign. He was mortally wounded later that year in the Shenandoah Valley during the Battle of Opequon, otherwise known as the Third Battle of Winchester, when he was struck by a shell fragment. He was brevetted major general in the regular army in the field. He is buried in Salem, New York, in Evergreen Cemetery.
The Russell's Brigade Tablet is located a little past the midpoint of the very short Howe Avenue and is on the left or north side of the road it traveling southeast toward the cul-de-sac. As a point of reference if traveling north on Taneytown Road, and if at the intersection, a left turn is Wright Avenue and a right turn is Howe Avenue. The tablet stands next to the 6th Maine monument. There are a string of monuments on the same side of the road. 
Parking is available at the end of Howe Avenue in the cul-de-sac. There is no other room to park on this road as there are no shoulders and it accommodates two way traffic. I visited this site on Monday, July 1, 2013 on the 150th anniversary of the Battle of Gettysburg @ 1:08 PM, EDT & @ an altitude of 470 feet, ASL. As always, I used my trusty and oft abused Canon PowerShot 14.1 Megapixel, SX210 IS digital camera for the photos.
The monument work was done under the direction of the Gettysburg National Park Commission (established by the United States Department of War), after they took over the administration of the park from the Gettysburg Battlefield Memorial Association (whose funds had expired) on March 3, 1893, and whose stewardship was then transferred to the National Park Service in 1933) SOURCE. According to the NRHP narrative, this monument was built in 1911 but finished in 1912, which according to my experience is questionable. I can't resolve if the 1912 date represents a completion of the physical construction of the tablet or an installation date. Other sources have it at 1910 & 1912. Another source wrote the last of the Confederate Brigade tablets was completed in December 1910. I don't know if anyone actually kept exact records of when these things were installed.
These battery tablets were cast by Calvin Gilbert. 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 and lived an amazing life.
There is an excellent excerpt in the American Guide Series about Gilbert attending the 75th reunion anniversary.
Look carefully on the reverse side of one of these tablets and his name might be there; I found a tablet or two like this. This one of course is devoid of his name. The inscription on the monument reads:
Army of the Potomac
Fifth Corps First Division
Second Brigade
Col. Jacob B. Sweitzer
9th. 32d. Massachusetts 4th. Michigan
62d. Pennsylvania Infantry
July 2 After 4 p.m. moved from the Baltimore Pike near Rock Creek with the Division left in front to support of Third Corps line. Third Brigade was detached to occupy Little Round Top and the Brigade crossed Plum Run followed by First Brigade and went into position on the edge of woods west of the Wheatfield facing partly toward the Rose House First Brigade on the right. Brig. Gen. Kershaw's supported by Brig. Gen. Semmes's Brigade having attacked this position and First Brigade having retired the Brigade retired across the Wheatfield Road and formed on the north side of the woods facing the road when by order of Brig. Gen. J. Barnes the Brigade advanced to the support of First Division Second Corps and engaged Brig. Gen. Anderson's Brigade at the stone wall at the south end of the Wheatfield but the supports on the right having given away the Brigade was attacked on the right and rear and it retired under a heavy fire to a line north of Little Round Top and there remained until the close of the battle.
Casualties. Killed 6 officers 61 men. Wounded 26 officers 213 men. Captured or missing 1 officer 120 men. Total 427.
There are hundreds of non-sculpted monumentation for the various Confederate States & Union units which fought at Gettysburg. There are about 10 different variations of tablets, markers and monoliths by my reckoning. Six designs represent brigade (2), division (2), corps (2), & army headquarters (2), each different in a subtle way so as to distinguish between armies. Battalion/ battery / advance position markers and regimental monuments for United States Regulars & Confederate have their own distinct design (2), bringing the total to ten designs at the battlefield. The bronze tablets (the brigade monuments) were created by Albert Russell & Sons Co. of Newburyport, Massachusetts. The granite bases which accompany the various tablets were created by the Van Amringe Company out of Boston, Massachusetts. The cast iron tablets were of course manufactured by the aforementioned Calvin Gilbert. The 1910 Gettysburg Commission report lists the awarded contracts to these companies (not Gilbert) for the tablets. All of these tablets were designed by architect Colonel Emmor Bradley Cope (July 23, 1834 - May 28, 1927). He designed pretty much every tablet for both the Union and Confederate armies, each one distinct, with several different varieties. He is buried in 
Evergreen Cemetery in Gettysburg, as well he should be as this park and most of the things seen here today were designed by him and as such, are his legacy. These monuments/tablets were erected just after the turn of the century during the first and beginning of the second decade of the 20th century. Each one has since been preserved or restored at least twice since the turn of the 21st century. The plaques and tablets were erected by the Gettysburg Park Commission (established by the War Department). The Gettysburg Park Commission is also referred to as the Gettysburg National Military Park Commission or the Gettysburg National Park Commission, to clear up any confusions, especially my own.
On October 1, 1898, the Gettysburg National Park Commission in a letter to the Secretary of War set gave recommendations for continuing the task of organizing and progressing the work of the Gettysburg National Military Park. Every November they wrote their annual report which outlined the work of the GNPC for that year. The following is an excerpt from that report relevant to this waymark. The link at the end of the paragraph will take you to the entire report. The method of marking the positions of troops on this field, as approved by the War Department, is to place the principal tablet or monument of each command at the position occupied by the command in the main line of battle, and to mark the several important positions subsequently reached by each command in the course of the battle by subordinate and ancillary tablets, with appropriate brief inscriptions giving interesting details and occurrences and noting the day and hour as nearly as possible. SOURCE
Most of the Commission reports have been digitized and can be found HERE. The initial 1893 report up to and including 1921 can be found here. 1922 to 1926 are missing and have yet to be discovered. The years 1927 to 1933 were discovered in 1996 and are also included. To my knowledge this is the most comprehensive list of documents that illustrated the development and formation of the park.
Information about these specific types of monuments:
BRIGADE HEADQUARTERS MARKERS (FOR UNION & CONFEDERATE TABLETS)
The Brigade Headquarters (and Confederate artillery battalions, equivalent to Union artillery brigades) are bronze tablets mounted at an angle on a stone pedestal and describe the movements and itinerary of each memorialized unit. Union headquarters have rounded tops and square bases. Confederate headquarters have flat tops and round bases. Union headquarters are marked with their corps or service branch symbol (like a cross, clover or crescent moon), while Confederate headquarters are simply labeled "C.S.A.". There are seventy-four brigade markers at Gettysburg honoring the Union's various brigades. (Other sources say there are seventy-five). There are sixty-four brigade markers honoring the Army of North Virginia's various brigades. The Union Brigade tablets consist of sea-green granite with a square 36” x 36” base; they weigh 3500 pounds. On each pedestal is mounted a bronze tablet with rounded corners weighing 300 pounds. They were built by Albert Russell & Sons Co. of Newburyport, Massachusetts and Charles Kappes. The Confederate Brigade tablets consist of red circular Maine granite bases 34 1/2 inches diameter and weighing 3,000 pounds. On each base is mounted a 300 pound bronze tablet. They were built by Van Amringe Granite Company (pedestals), Albert Russell & Sons Co., Newburyport, Mass (tablets) and Charles Kappes (foundations). SOURCE & SOURCE
The Russell's Brigade - US Brigade Tablet is a contributing feature to the Gettysburg Nat'l Military Park H.D. which is nationally significant under NR Criteria A, B, C & D. Areas of Significance: Military, Politics/Gov't, Landscape Architecture, Conservation, Archeology-Historic. Period of Significance: 1863-1938. The monument is designated as structure no. MN496.
From the Nomination Form:
1 of 75 Civil War US Brigade Tablets in Park. Records movement & itinerary of Russell's Brigade during the Battle of Gettysburg, July 1-3, 1863.
Short Physical Description:
Bronze inscription tablet, 4”0’ x 3’8”, attached to slant face of polished sea green granite monolith. 3’0” squared base of monument tapers to a smaller dimension at the tablet. All 5’4” H.
Long Physical Description:
Located on N side of Howe Avenue.
Source
1. NRHP Nomination Form
2. Draw the Sword
3. Virtual Gettysburg
4. Stone Sentinels
5. Historical Marker Database