A friend of mine maintains they are but I disagree. Certainly they look the same & are both nominally 20mm wide, but I'm not sure that means you can swap them? Anyway, what would be the point, given that they look the same? He mutters obliquely about clasp comfort & taper vs constant width but is not really clear why he wants to do this.
To clarify, he's looking to put a 2254 bracelet on a 2016 42mm Moonwatch.
We've agreed that if even one person agrees that it's a) possible & b) sensible, I have to buy him a beer. If nobody agrees he'll admit defeat & beers are on him (never known him admit defeat yet). The stake is irrelevant really, I just want him to be wrong!
In your own time, go on...

 

Well, you have both watches in your avatar, have you given it a shot yet? You can show your mate there and then and start drinking the beers, regardless of who is right.

 

It's true I've got both but one's on a NATO & the other on a Steveo Straps leather strap. I might try it though, the bracelets are in the boxes, I'll dig them out over the weekend.

 

I have both. The bracelet links are interchangeable as I have a Seamaster half link on my Speedy bracelet, the end links do not fit. They appear identical but its curve is slightly different as the case size is slightly different, even though they are both 20mm lug width.

 

The distance of the spring bar/lughole to the case is another reason it may fit badly.
It's Friday, just have the beers.

 

Winner! I'll stroll down the pub after work & collect my winnings. I'll look forward to my mate's next watchmaking brainwave...

 

Not so fast mate .You owe Him a beer.
The 1610/930 bracelet DOES fit on a Speedmaster case, I've done it.
Why? Because I needed the divers extension on the clasp to get the watch over my huge hand and still be a fairly tight fit on my skinny wrist.

 

Pictures or it didn't happen you know the drill ..