Unique Model 52 (I think!)
Probably a Triple K repro
Unique Model 52 22LR 10RD MAGAZINE 383M | Handgun Grips
You have to wait for a sec or two for the pic of the magazine to actually appear in the ad for some dazzling reason. Then click on the pic for a bigger view.
Not exactly cheap either!
IIRC, these won't fit the more common JC Higgins Model 85 / Unique D2 (?)
About an 1/8" difference in OAL length of the mags and they won't lock in place correctly when switched with the heel style mag latch used on both pistols.