Carl Vincent has sent this in, and so we've decided to create the ARTIFACTS page series to share with you those many things which are in 'private collections'.  Carl writes:

It is an enlisted mans branch insignia disc, (a little bit bigger than a quarter.) I have had a collector (who claimed to be an expert) take a look at this piece. He told me it was a WWI US EM Coastal Artillery Disc. (I had already figured that out.) The background is done in a very tiny checkerboard which is only visible upon close inspection. He told me with this type of background made the disc one of the more rarer types.  It has a screw back, which is bent and no longer serviceable. The depiction on the front side has 2 crossed cannons. Where the cannons cross is a circle with the silhouette of a shell standing on it's end. On the bottom of the disc, centered between the lower cannon ends, is the letter "C". The entire disc is colored in subdued brown or black paint. About 40% of the paint remains. I would really like to know more about it. I found it near the Post Theater when I visited Corregidor in 1980.  The collector did make a nice offer to buy the disc, but it's not for sale. Based on what little I know about it, I think it might have been lost in the 1920's, only to resurface when I found it.

My guess is that the "C" stands for Battery C. If so, it was not WW1 vintage as the Coast Artillery did not have lettered batteries until about 1924 

- George Munson  -