My thanks to Hans and mbl1230 for posting the above.I only have the SRS books which date from 1994. Here is a link to an archived listing for No. 390:
Collectors Firearms Archives - Home
I did get to handle this gun at a local show back in the '90s, and it had the documentation with it. As you can see, it is a well used piece and it appears as though the muzzle is somewhat worn back toward the loading lever latch, possibly due to jostling in the holster during cavalry skirmishes.Speaking of holsters, yours is of the type known as a half-flap, and may be a period replacement for the war time issue holster, especially if the trooper took his revolver home. The 2nd Ill did report having "navy-sized Holsters" which the standard cavalry style holsters,but shorter for the 7.5 inch Navy barrel rather than the 8 inch Army barrel.
The 2nd Illinois Cavalry was pretty well armed throughout the war, compared to some other units. They were issued Colt 1851 and 1861 Navy revolvers, Sharps carbines, and M1840 Dragoon sabres and pretty much stayed with these during the war, although Burnside carbines were issued towards the end (two are known with SRS records). A Google search of the 2nd Illinois Cavalry will turn up both info and photos,some iwth troopers holding their 61s.
I'd definitely suggest getting a Colt Factory letter, in addition to seeing what SRS can do. If you get some more photos, please post them.
Hope this little bit helps.
Regards,
Tecololte