According to MWO, it has remained uncertain whether the Naiad crown was originally meant for the Speedmaster. I'd prefer the A-1 flat foot 24-tooth crown, especially when you are willing to bid up against the current price..
There are two different crowns in the OP post, first has 24 teeth and misses the long tube and second crown has 26 teeth and is on sale on eBay.
Imho the second crown is the right one. Even if MWO says it should have 24 teeth.
Now how much will it cost ?