where to post pix? Its likely a Nazi era based rifle 1933-45, but what we can see today puts it more in the 1945-Postwar use category, as that’s certainly when the barrel, stock & sights were done. You could also post it in the ‘Collecting off-topic’ forum, really no wrong place, if a moderator feels it belongs in a different category, I believe they can move the thread. try to keep image size @ < .5mb to upload here.
are there any original marks on top of or on the right side of the receiver? It appears scrubbed & new serial number applied. Or, might the seller provide any info, perhaps the smith’s name that did the barrel, stock & sight work? The German inspection marks can steer us in a direction as to date, if any are left on the actual receiver. the trigger guard & floor plate have inspection marks, but don’t share the receiver s/n, so likely just random parts used.