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.