[Help] 3541 with a 3445/9445 caseback - Franken?

Hi everyone,


Could you help me identify this Patek?

I got a deal from a local seller but!

The case looks like a Ref. 3541, with the straight lugs, but the inside of the caseback is stamped 327387 / 9445 or 3445


Could this be a genuine 3541 with a replacement caseback, or is it more likely a Franken?


Has anyone seen that case before?


Thanks!