It didn’t sold for 3800$ and of course it is a legit zf41 byf43 . I agree the scope and mount is not numbered to the rifle ( wich is not that uncommon . Original
Base looks legit, marked 135 and the stock relief looks correct as well.
Scope/Base was maybe just added as it does not appear numbered matched to the rifle (early byf ZF41's should have the mount matched to the rifle I believe). However, there is significant glare where it should be marked.
Stock is sanded - likely when the duffel cut repair was made (weird place for a duffel cut).
Very surprised this sold for $3800 CDN within a few days....likely because people sell RC's for $1400-1600 CDN these days in Canada - which is nutz - people don't realize they could import a Bolt MM for those dollars and maybe even luck into a matching rifle from the US.