This Mossberg manufactured S130 series receiver peep sight dog spring screw is for the model 42MB(a) bolt action rimfire rifle and is in very good condition exhibiting a mixture of original blue finish with a brown patina and having some specks of surface rust present. (file photo)
Note: Mossberg model 42MB(a) bolt action rimfire rifles with the following serial numbers have been observed with this part: 38952
