Thanks David, was a misunderstanding on my part, I had been to that page before. For some reason I expected to see "accession card" written out, and also a photo of the other side, but I was expecting too much or too specifically. Anyway, here's all of what's on the page I got to in case anyone else has trouble with it:

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ACCESSION NO.: 1990.100.7
NOW LOCATED: Object on display in galleries
DATE: First half 19th C.
SUBJECT/CLASS: Signal guns
Signals and signaling
Maryland-Steuart Collection
United States -- History -- Civil War, 1861-1865 (ASSOC.)
Confederate States of America. Army (ASSOC.)

DESCRIPTION: Confederate Signal Pistol, English make, brass frame and barrel, belt hook on right side, steel ring in handle. About 31 calibre, 2 1/2 inch barrel, 8 inches overall. On left side of frame; "W.D." and British broad arrow, "C.S." in large letters and "Carolina."

Length: 6.35 cm (2.50 in)
*Length overall: 8 in; 20.32 cm

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I got a direct reply from Royal Armouries today, but I can't disclose any of it due the lengthy disclaimer/warning which is on the email (the government lawyers earning their pay of course!)

However I can safely say that I have no new information to add to what Mike Carrick already provided.