This is a 7 shot Lowell Arms Revolver chambered in .22 Short. 

1) 77mm (3⅛") octagonal steel barrel

2) Nickel finished brass frame with spur trigger.

3) Top rib marked, “Made for Smith & Wesson by Lowell Arms Co, Lowell, Mass.”

4) Brass frame marked, “Pat April 2, 1867”

6) Bottom rib marked “Venables, Oxford”

7) Cylinder faintly marked, “DEC. 18 1860”

8) Birmingham proofmarks on barrel and cylinder.