Introduction + Questions on Seamaster

Hello OmegaForums! Picked this Seamaster up recently and am a bit perplexed with it. Right off the bat I know it (to my knowledge) may be a bit of a frankenwatch but I would really appreciate some insight. While the cal1010 movement has a 42,xxx,xxx,xxx serial, the case back was replaced with a ref 166.2020 case back. Additionally was the cal1010 movement ever in day date? As I continually find only date. I'm unsure if its been a redial, however I dont think the lumes at the hour markers are factory either.

Thanks so much for the help!

Exactly what I thought, a random hodgepodge of parts thrown together.

Welcome to the forum. I hate franken watches because they can trick you very easy. I also bought several in the past. I also seen that the screw which hold the mechanism it's missing.. which is also a red flag.