Professor
·Found another Railroad Official Standard ref 135.005 w/ manual winding cal 600. SN is just a few away from a previous one aquired couple years back. These usually have four digit case number on the outside of the case back below the hippocampus. This one is a tad unusual and has case number between the lugs.
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I'm guessing these are insanely accurate. Whats the original specification for accuracy of this sort of watch?














