This is the most interesting thread I've read in a long time. Thank you to Ollie and M4tt (and Broussard!) in particular for their research and for taking the time to post their findings.

Quote Originally Posted by M4tt View Post
Sure, but the point is that every Rolex of the period had the precise year and quarter stamped on it. That Rolex changed the designation of the case is largely irrelevant. It’s the same 35.5mm case housing the same movement but with minor dial variations. In fact, the 6150 is meant to be the first explorer, made to celebrate the ascent, so that’s another bit of Rolex BS uncovered as clearly the 6150 existed in Q1’53.

For Stahl’s conjecture, what would matter is if there was a redacted date. There isn’t. Now, it is possible it’s a Franken faked by Gregory (from whom ultimately the provenance comes) but if we are accepting that level of scepticism then pretty well anything goes.
Just thinking out loud: could it be possible that Rolex prepared new, engraved case backs after the ascent turned out to have been successful, so they could swap the unmarked original case backs at the earliest opportunity? That would explain the 'wrong' date and model number on what could in fact be the '52 issue watch.