How To Spot Frankenwatches?

So I have my eye on a couple of Speedmasters on ebay and want to make sure I get a decent deal. To that end, I have two questions:

1. What are the strongest indicators of a frankenwatch? I know to look for an OEM crown and case back. But how does one match up the serial # on the movement with the rest of the watch?
2. When I see discussion of redials on this form, it is mostly in reference to Seamasters. Are Speedies as likely to be redialed?

As a very very new collector, I might be willing to snag a redial if it is cheap enough, but I am still getting my head around the complexity of this obessi, er, um, hobby.
TIA,
Lex

With Speedmasters it's more likely that the original dial has been replaced with a later version. The early ones had applied Ω logos while later versions had the logo in white ink. Can't tell you when this changed but I think it was about the same time the 321 was replaced by the 861, meaning around 1968 or so. There's also small tells about the bezel's originality too. There are a few members here very versed in spotting Speedy frankens so wait for them to chime in.

Can I mention that this is an extremely nerve-wracking hobby? 😁 Thanks for the input!

I think you just did. 😉

Don't worry, we got your back. Just remember to ask here BEFORE you buy.