There were 3 Railroad Specials: the 50, 51 and 52:
50: All stainless steel
51: Stainless steel with a 10K GF bezel
52: All 10K GF case and bezel
All have a 505 movement but with a micro-adjuster on the regulator for more accurate timing.
The 52 seems much rarer than the other two. The 51 is very similar to the
Hamilton Clearview.