Speedmaster 105.012-66 at Bonhams today!

Agree with your assessment on the condition and parts and price seems to line up with William's "fair" range for head only. Having a bracelet is a bonus. For me it's tough to discern what the colors would be like in real life from these pictures, but the dial looks like it's got some attraction to it and probably the standout part of this watch. Looks like it's a watch that's well-lived and well-used -- shame it didn't become a family heirloom which I think would be a more appropriate fate for it.

I think this is the first time I've seen a Speedy stay within its price estimate!

One would think that looking at something like a vintage 321 Speedy, you'd at least be armed with enough knowledge to spot a modern bezel. Seeing in person, at worst you might be briefly taken in by the aged look thinking it all goes together, but upon closer inspection you're surprised that it's a new one. The pics probably make it more clear that it's replacement...just a hunch. I agree that doing this aging is nefarious, but on the other hand I think it would look worse with a shiny, new bezel. At least it looks like the bidders were savvy enough to not make this a high dollar auction.

4850 GBP is still no small sum which makes me wonder who buys this type of watch. A discerning collector would probably not be interested or prefer a very nice 145.022 at near the same money. Someone who isn't as knowledgeable or just wants an affordable 321 Speedy I suppose could be the target buyer (hence the issue with the bezel), but again, I'd think they'd go for something in better shape for that kind of money. I think these low-priced 321s sit in a weird spot in the market; relative to purchase price more finicky to service (vice an 861) and more expensive. It only takes one or two people interested to buy it I suppose, and yes, it does have a nice dial so there's that.