Hi Ian,

Thank you for contacting Mearto with your appraisal inquiry.
A couple of prints from this edition have sold at auction in the past 10 years, as follows:
($500 in 2013) https://www.liveauctioneers.com/item/19996398_paul-pletka-gac
($140 in 2016) https://www.liveauctioneers.com/item/46873441_paul-pletka-gac
Based on the photos and information provided, and subject to examination, this is:

Paul Pletka (American, b. 1946)
"G.A.C." (George Custer), (undated)
Lithograph print
edition #12/25
17 x 22 inches, matted and framed
Signed Pletka, lower right
PROVENANCE: acquired at auction in the late 1980s
$300-500*
*represents a fair-market value for auction purposes; retail or asking price may vary.