Typically the serial numbers for all components will match, but not always. As an example I’ve got a Bally Star-Jet where the playfield serial number is a couple of digits off from the rest of the game. It came from the factory that way. My personal thought is that you should just replace the playfield if it’s a better one and not worry about it. I don’t think it’s a big deal and I’m pretty sure most collectors would agree. The original vs repro is a somewhat different argument but as long as it’s an original playfield I don’t see any issues.