I just got another one of these (w/base) in the mail today for my long-barrel P-38 project so I thought I'd update availability...
This sight can also be found/listed as OEM on the following rifles -
M24/30 FN MAUSER CARBINE REAR SIGHT
M1922 CHILEAN CARBINE REAR SIGHT
Chilean M1895 Short Rifle Rear Sight Assy
Chilean M1895 Carbine Rear Sight Assembly
Graduated to 1400 Meters
There seem to be a goodly lot being sold in the white, unused. packed in cosmoline.