Graphic Art Based on a Black and White Photocopy

Obverse Design First line "GEN. MESS". Second line "1619". Third line "S/M BASE". Last line "COCO SOLO, C.Z.".
Reverse Design Blank.
Metal Brass Size and Shape Oval 30 mm high and 38 mm wide. Round hole near the left edge.
Dates Issued Unknown. Anytime between 1918 and the 1960's, but probably close to 1918.
Issurer S/M Base in Coco Solo. Coco Solo was a U.S. Navy submarine base established in 1918. By the 1960's no vessels remained, only some support staff and housing. The "S/M" most likely is an abreviation for "Submarine".
Numbers Issued Pieces in collector hands include #1619.
Rarity Very Rare. Manufacturer Unknown. Source Plumer Collection.
Varieties None known.
Function Unknown. Perhaps used as identification when going for meals (general mess) at this military base. I would appreciate e-mail from anyone who can add anything to the history of this piece.
Population Count Known specimens are as follows:
  1. Check #1619 - Warren Lloyd Plumer Collection (simulated above).