I used to think Railmaster and Aqua Terra, are and always were two independent sub-collections in Seamaster. Whye does caseback of this Railmaster say "Aqua Terra" ? Ref. 2806.52.37, currently there is 8 watches for sale, https://www.chrono24.com/omega/ref-28065237.htm All stamped "Aqua Terra".. Why?
that's like asking why the Planet Oceans only say that on the back in the same manner but only Seamaster Professional up front (also applies to all Aqua Terras ever)