This Ruger manufactured complete mainspring housing assembly is for the Mark I semi-auto pistol and is in very good condition with light wear. (file photo)
Note: Ruger Mark I semi-auto pistols with the following serial numbers have been observed with this part:
No Prefix: 127144, 129129, 166765 & 210887
10-90939
12-11122
16-58723
17-33228
