SM300 (14755-62 SC / 165014-62)

The insert font is wrong, that's why it's a repro. The knurling on the bezel is also incorrect.

If I remember correctly, 2913s and early 14755s had countdown bezels, which is why you'll see some authentic count-down bezels rather than the now-standard count-up.

You'd really ought to do thorough due diligence in advance before you go around buying pieces as "investment". Even if this double-stamped reference were to appreciate over the coming years, its condition alone would ensure that this particular specimen would not nearly appreciate as much, if at all compared to an exceptional example. The service crown, pitted gasket channel, and mismatched movement plates are all causes for concern. If I were purchasing this for my own collection, I wouldn't think of going near this piece unless it was priced as a parts watch.
Correct, exceptional examples do exist. You just need to have the self-restraint to save and wait until you spot one.

Double-stamping on Speedmaster casebacks usually indicates an "upgrade" up to that reference, so it's possible that the dial and hands of this 14755 were swapped to tritium 165.014 types. The bezel would also have been changed to a count-up, I suspect. Some time later, the dealer probably replaced the bezel and the dial to make the watch more presentable as a 14755.