i understand the Seamaster 600 Ploprof came in 3 dial variations but I have yet to understand why there are two different reference numbers for this watch. Can anyone clarify?

 

There aren't. Update of numbering system adds an extra zero...

 

Thanks Al. Did the case design remain unchanged during the various dial variations and numbering system change?

 

There are 5 or 6 dials, 5 or 6 bezels, 3 or 4 hands sets, 2 or 3 cases...
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The important point here is that cases that are stamped 166.0077 are service cases, original cases are only stamped 166.077.

 

Did the Ploprof ever come in left handed version i.e. crown at 3 and release button at 7 o'clock?

 

No, but some sellers will tell you it does...

 

True indeed.