I saw this lovely Railmaster for sale on the sale page:
https://omegaforums.net/threads/omega-railmaster-2504-52-36mm-version.26904/

and I noticed on the back it says its a Seamaster Aqua Terra....is a railmaster a seamaster aqua terra?

 

http://www.omegawatches.com/collection/seamaster/railmaster-chronometer/25045200

 

Yes, sort of. The Railmaster was part of the original Aqua Terra family that was launched around 2003-2004. Same bracelet and case and base co-axial movement (the no-date version of cal.2500).

 

Looks like someone beat me to it, shucks.