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It would fit a flat sided receiver just under an inch thick. Center of the pivot screw to center of the elevation clamp screw is1.25". Perhaps one of the various slide action .22 rifles?
Tried the screen shot search as you suggested. Thanks for the lead.
Might be a Winchester 80A sight.
The small screw that secures the scale plate isn't in line with the two larger screws that actually mount the sight. A bit awkward on a round receiver?
Switzers Auction has a M72 Winchester. Enlarged the photo of the left side of the receiver. The stock is inlet for the sight, and the three holes are there.
Have a gander in the EE, rimfires for sale.
Member Cbob has a Winchester 69A for sale with what appears to replicate your sight.
Has the third screw too.