[Amps] 4-1000A Date Codes

[AB5MM]

I have searched both high and low, but can't seem to locate any 
definitive answers as to how to decipher the date codes on a couple of 
Eimac 4-1000A's here. Can someone help me out? They are P8-10539 and 
CRG-108. The first P8 code is hand written on the metal base inside with 
a vibration marker. The CRG is in the same approximate location on the 
other tube, but is neatly stamped.

Any help would be greatly appreciated.

Thanks and 73,

Steve
ab5mm