Got one fer the experts here

[Presidio]

Recently came inta my possession a 1851 Navy Sheriff w/ 5 1/2" brl., .36 cal in Brass Frame.  Think it's a Uberti or other than Pietta.

Here's the catch....or actually a lack of one.

With the hammer fully in the down position (or fired position), you can still rotate the cylinder by hand easily and it will push the hammer up out of the way for the rotation with no hanging what-so-ever.  Also, when same hammer is in cocked postion, cylinder will rotate either direction freely with no drag what-so-ever.

Okay, I know its' broke...but, can ya'll point me in the right direction as far as repairing it - or should I just go ahead and hang it on the wall fer decoration...(which is what I originally bought it for, cause my main calibers are .44bp & .45lc).  Just thought I'd give it a try and tinker with it some.

BTW - the cylinder threads appear to be slightly worn out as well on the cylinder bolt.

This is a brain picker for you, Cowboys...Make me proud!

[Will Sellit]

Since you asked for an experts opinion there is no way I should be responding, but my guess is it has a broken bolt spring. This is the flat spring that Colts seem to be notorious for breaking. If you check with Brownells I am quite sure they can fix you up.
Now the experts will respond and tell you what really is wrong.
Good Luck.

[Presidio]

Thanks fer the quick response, Will.

Yep, I kinda figured it might be the spring - I just ain't never seen it do that before

BTW - I found some markings on the left side of the frame:  It's an "A" over an "M".  I got no clue as to who the manufacturer is. 

Like I said, Folks.  This is a tinker toy as of now and all fer experimenting on...

[Wild Ben Raymond]

Howdy! I thing the A over M is a Army San Marco's, I at one time had one of their early 51' Navy's It was the worst gun hands down, I ever once owned. Steel was soft, it never made it through a match without having some problems. I don't know what their quality is now but I think it's gotten better. Wild Ben Raymond

[Chance]

Sounds like you have two problems, Presidio. Firstly if the cylinder is not locking in place then as has been suggested the trigger and bolt spring is broken. If you can turn the cylinder both ways then the hand spring also seems to be gone. Both are a simple fix costing you no more than a few dollars. There should be other marks on the pistol which will help identify the maker. It is definitely not a Uberti as they have not made a brass framed Colt (neither did Colt).