I don't think I'd heard it was non-screw-down before, but I'm really glad it is.
I have a daydream about taking one of these Railmasters and fitting in the manual-wind movement from the Hamilton Khaki Field Mechanical - they're both Swatch Group parts so IMO Omega really should have used that for the Railmaster. I don't nearly have the fabrication skills required for that though but maybe someday if I have tons of money to waste, I'll ask someone to do it.
I used to protest about how the Railmaster Trilogy should have been a manual wind movemen like the original, but then I thought about it more and stopped complaining because of the following:
1) Omega was able to install a state of the art automatic A-magnetic movement without changing the original dimensions of the Railmaster
2) as much as I would like to manually wind my Railmaster everyday, I do admit that an automatic movement is always more convenient because...we occasionally forget!
3) Correct me if I'm wrong (please do!), an automatic movement is usually more accurate when compared to a similar movement without a rotor, and the dead-on accuracy of this watch is one of amazing characteristics---and to your suggestion...I'm not sure that fitting the RM with a Hamilton Khaki manual movement is worth it's merits....and like I said, if you want to wind it manually, go for it!...you certainly can power the mainspring by winding the crown, you just don't NEED to!
4) Finally, I cannot help but think that if Omega could have fit an automatic movement in there in 1957, they most certainly would have done so...after all, this is a professional, "Master" level watch. But since they needed to make room for the soft iron Faraday shield to achieve anti-magnetism, they didn't want the watch to be so thick and top heavy, so they decided to do away with the self-winding rotor.
So in 2017 when they had achieved the 8806 automatic movement that can withstand 15,000 gauss without the need for Faraday shielding, they accomplished something closer to the original intention with the Railmaster in a reasonably compact case design.