This Mossberg manufactured red synthetic button with the white printed "F" on the top is the piece that mounts into the walnut stock just behind (under) the safety lever and assists in indicating which position the safety lever is set at. This part is for the model 42MB(a) bolt action rimfire rifle and is in very good condition with light wear and will likely need an epoxy to help hold it in place. (file photo)

Note: Mossberg model 42MB(a) bolt action rimfire rifles with the following serial numbers have been observed with this part: 38952