2nd Pennsylvania Heavy Artillery
On a field of red satin cloth, the gold crossed cannon signify that the regiment was of the artillery service branch, and the blue number two (2) for the 2nd Pa Heavy Artillery.

The lower enameled metal pendant reveals the Corps history of actually two units.  The 2nd Pa Heavy Artillery regiment was such a large unit that it was divided into two separate regiments:

April 20, 1864
New regiment formed from surplus recruits, "Second Provisional Heavy Artillery" and assigned to duty with the 9th Army Corps.

Thus, the pendant has the red shield with crossed anchor and cannon of the 9th U.S. Army Corps for the "Provisionals", and the red diamond insignia of the 18th U.S. Army Corps for the 2nd Pa Heavy Artillery.  The body of the pendant, a blue heart, represents the 2nd Pa Heavy Artillery's affiliation with the 24th U.S. Army Corps after the fall of Petersburg.  The gold outlines of fortifications, also attached to the blue heart, represent the units service in the fortifications surrounding Washington, D.C.

This recreated drawing was taken from an illustration which appears in the book History of the Second Pennsylvania Veteran Heavy Artillery, (112th Regiment Pennsylvania Volunteers) From 1861 to 1866 by George W. Ward.  This is the ribbon which is presumed to have been awarded to the surviving regimental veterans at their 1900 reunion.