I am taking a stab in the dark that this is indeed the Rumford Model as I cannot find any adverts with this on. The crystal this takes seems to fit two models according to GS catalogues, the "Hadley" and the "Rumford". Indeed they look near identical but this model has different lugs (see Hadley watch also listed). If anyone has any better ideas as to the model please let me know and i'll update, for the time being it will be listed as the Rumford.
Good ad find. So now w/ this ad and crystal data, do we have at least three possibilities for this crystal? Rumsford, Hadley, and perhaps the third previously unknown crystal is the Brixsome?
I'm good with Brixsom for subject watch, and will check other entries in watch database for the "other two" which may be either Hadley or Rumsford....but could arguably be unknown.