Hi Brett,
I pulled out an old copy of MIL-S-13949.  From what you have provided, I
believe the materials are described as follows:

     FL-GB .062 - 13949/2 plastic sheet, laminated, metal clad, base
material GB, glass base, woven, majority polyfunctional expoy resin, hot
strenth rentention, copper-clad with thickness .062"
     FL-GE .062 - 13949/3 plastic sheet, laminated, metal clad, base
material GE, glass base, woven, majority difunctional epoxy resin, general
purpose, copper-clad with thickness .062"

Hope this helps.

Steve Sauer

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