The 6th Maine Artillery, Battery F was also known as Dow’s Battery (This is also written on the front of the monument). During the battle of Gettysburg, the unit served as a member of Taft’s Brigade in the Artillery Reserve, Army of the Potomac. The 6th was commanded by Lieutenant Edwin B. Dow (1835-1917), a clerk from Portland. Dow was wounded at Cold Harbor. Under his command were 103 men and 4 Napoleon cannons and among the men, 13 were wounded.
Born in Canada young Edwin Dow
was a 26 year old Portland, Maine
resident when on February 6, 1862
he was commissioned 2nd Lt. in
Freeman McGilvery’s 6th Maine
Battery. He would rise to the rank
of Captain and at Gettysburg his
name would be etched in stone as
commander of Dow’s 6th Maine
Battery. SOURCE
From the Historical Marker Database, Craig Swan: Dow's Battery was Battery F of the 6th Maine Light Artillery. It was commanded by Lieutenant Edwin B. Dow and was part of the 4th Volunteer Brigade, Artillery Reserve. Dow was attached to McGilvery's 1st Volunteer Brigade during most of the battle. Thrown into action on July 2 as the Federal Third Corps withdrew, the battery fought east of the Trostle Farm. Later it relocated on Cemetery Ridge, where it participated in the actions of July 3. The battery brought four 12-pounder Napoleon guns into the battle, and lost none. Eight men of the battery were wounded, and five horses were lost. SOURCE
The 6th Maine Battery Left Flank Monument is located on the left or west part of Hancock Avenue if traveling north toward the Pennsylvania Monument which looms hugely in the distance. This part of the battlefield is the south section of Cemetery Ridge. The primary 
6th Maine Battery Monument is flanked by a couple of 12-pounder Napoleons, which apparently are not Napoleons but 6-pounder Field Guns altered to resemble 12-pounder Napoleons in the 1890s. This flank marker is to the left or just south of the primary monument, 66 feet away. 
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 5:31 P.M. I was at an elevation of 550 feet, ASL. I used a Canon PowerShot 14.1 Megapixel, SX210 IS digital camera for the photos.
Often, state regiment monuments are also accompanied by secondary monument which designate positions maintained from July 1-3, 1863 as well as flank monuments to delineate the ends of troop lines. Presumably, the position markers were dedicated at the same time as the primary brigade monument, October 3, 1889. The flank marker is composed of granite, smooth on all its rectangular prism sides, and, with the incised inscription found on the slanted top. The marker are all LF & RF 1'x1'6"x1'10". Additional details from the nomination form concerning the flank monuments may be found below in red. The inscription reads:
.......
6th ME. Battery
July
L
The 6th Maine Battery Flank marker and Monument 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 collectively identified as structures number MN270-D.
From the Nomination Form:
1 of 15 Civil War Monuments to Maine of the GBMA Era (1863 - 1895). Indicates position held by Dow's Maine Battery morning of Jul 3, 1863 to 10:00AM Jul 5. LF&RF markers 60'&122' S-N, respectively. Mn has 2 flanking markers and 2 cannon. Located W side of S Hancock Avenue.
Short Physical Description:
Mn w/2 flanking markers and 2 cannon mounted on cast iron carriages. Base 6'sq x 1'6"H rough cut, tooled edge. 2 part tapered shaft, 1st bas-relief front, 2nd bas-relief front, incise inscriptions 4 sides. Top, 5 stacked cannon balls, black polished. LF & RF 1'x1'6"x1'10", chipped.
Long Physical Description:
Monument that has two flanking markers and two flanking bronze Napoleon cannon mounted on cast iron carriages. Monument is a two-part tapered granite shaft with a top containing five stacked black polished cannon balls and set on a six foot square rough cut base with a tooled edge. The lower part of the shaft has a bas-relief front and the upper part has a bas-relief front, with incised inscriptions on four sides. Flanking markers are 1x1.6 foot. Located on the west side of south Hancock Avenue.
My Sources
1.
NRHP Nomination Form
2.
SIRIS
3.
Stone Sentinels
4.
Virtual Gettysburg
5.
Draw the Sword
6.
Historical Marker Database