The 2nd New Hampshire Infantry served as a member of Burling’s Brigade in Humphrey’s Division of the Third Corps, Army of the Potomac, a Fighting 300 Regiment. 2nd New Hampshire Volunteer Regiment was the longest-serving volunteer regiment of the State of New Hampshire in the American Civil War. The 2nd New Hampshire was organized in early 1861 and mustered in June 4, 1861. The 2nd NH fought from First Bull Run until the occupation of Richmond approximately four years later. The regiment was led by Colonel Gilman Marston, a future United States congressman who represented the state in the 51st Congress (1889-1891). (Wikipedia - citation below)
The unit was commanded by Colonel Edward L. Bailey (1841-1930). Bailey was a clerk in the Manchester post-office. Bailey entered the 2nd New Hampshire as Captain of Company I. in June 1861 progressing to Colonel of the regiment in April 1863. At Gettysburg, the regiment served in Burling's scattered Brigade of Humphrey's Division, III Corps, and lost heavily in the Peach Orchard where Bailey was wounded. Bailey was later brevetted four times in 1867 for Williamsburg, Fair Oaks, 2nd Bull Run and Gettysburg. He was wounded at Williamsburg and again on July 2 at Gettysburg. He then served as officer in post-war regular army until dismissed by court martial in 1893. He was one of the longest surviving officers of the battle, living 89 years. He missed the 75 year reunion unfortunately. His unit had 354 men engaged at Gettysburg and among them 20 were killed, 137 were wounded and 36 went missing.
The 2nd New Hampshire Infantry right flank monument. The flank monument is located on the left or west side of Emmitsburg Road if traveling north, across from the southwest corner of the 
Peach Orchard and the entrance for the road which wraps around in a perfect square, Birney Avenue, back onto Emmitsburg Road. The flank monument is 99 feet, west northwest from the primary monument, directly across the street. "The right flank marker stone of the 2nd New Hampshire was placed near the Wofford Brigade Tablet on Emmitsburg Road. The 2nd New Hampshire was part of Burling's Brigade, which was the reserve for the III Corps in the Peach Orchard sector. The Regiment was advanced at least as far as the southwest corner of the orchard, facing south, before finally being withdrawn." (Craig Swan) 
Parking is available at enlarged shoulder sections on Birney Avenue at the Peach Orchard. I would stay off Route 15/Emmitsburg Road. Stay off the grass less you be ticketed. I visited this monument on Thursday, July 5, 2012 at 11:35 AM, EDT, & @ a 589-foot ASL elevation.
The monument was erected on July 2, 1886 by the State of New Hampshire. The granite monument is a little over a foot high with a peaked top. There is an inscription on the front, polished face. The monument is behind a split rail fence, stuck in the grass, overlooking the road. The flank markers are referenced and described a few times in the NRHP narrative for the primary monument. The parts concerning these monuments have red font to make it easier to find and can be found below. The inscriptions is incised in the granite, like it was done with a router. The brief inscription reads:
2nd N.H. Vols
R.F.
The 2nd New Hampshire Infantry Monument & flank markers collectively are contributing features 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 monuments are identified as structures number MN176-B.
From the Nomination Form:
1 of 4 mns in Park honoring NH commands in Gettysburg Campaign. Marks advanced position taken by 2 New Hampshire Infantry on July 2, 1863. Located on SW corner of Sherfy Peach Orchard near the junction of Birney Ave w/ Emmitsburg Rd.
Short Physical Description:
Rough-hewn base, 6'2" sq. Smooth granite shaft 3'3" sq. All 11'4"H. Apex top w/ reliefs of muskets pointing up at edges. Inscriptions in polished base. 2 Flank markers, 1'2"x1'2"x1', RF, apex top, polished w/ inscriptions, LF, flat top, polished w/ inscrip.Base 5'9" square. Shaft 4'5" in circumference, 17' high, fluted column topped with sculptured eagle. Inscriptions cut into base.
Long Physical Description:
Monument that has two flanking markers. Monument is a 3.3 foot square smooth granite shaft with an apex top that contains reliefs of muskets pointing up at the edges and set on a 6.2 foot square rough hewn base. There are inscriptions in the base. Overall height is 11.4 feet. Flanking markers are 1.2 foot square, polished with inscriptions of which the right marker has an apex top and the left marker has a flat top. Located on the southwest corner of the Peach Orchard near the junction of Birney Avenue and Emmitsburg Road.
My Sources
1.
NRHP Nomination Form
2.
SIRIS
3.
Stone Sentinels
4.
Virtual Gettysburg
5.
Draw the Sword
6.
Historical Marker Database
7.
Wikipedia