Gibson EM-200 serial number location

[Mandowacker]

I have a Gibson Florentine EM-200 Electric Mandolin but cannot locate any serial number after making a thorough search. It is a solid body. Can anyone help locate it?
Thanks for any help!

[Perry]

I had one with no serial number or it wore off...IIRC the fact that it was not stamped (otherwise it would not have wore off) indicated my EM-200 was mid fifties.

[jefflester]

Back of the headstock. If not there, could have worn off as Perry indicates.

http://www.guitarhq.com/gibson.html#serial
and scroll down to the "Gibson Serial Numbers, 1952 to 1961, solid body models" section.