This Ruger manufactured early variation unmarked (Pre-A100) grip frame with trigger guard is for the Mark I semi-auto rimfire pistol and has the magazine button flare on the right side of the frame. This frame is in very good condition retaining the majority of its original blue finish with the balance exhibiting a brownish gray patina and containing a few specks of light rust. (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 & 451514

10-90939