[Amps] 4-1000A Transmitting tube

[Jim Isbell]

I just acquired a 4-1000A and am wondering about its history.  It came 
in an Eimac carton and looks like it is unused as there is NO 
discoloration of the glass and the plates are a light gray in color. 
 But it is marked on the envelope as being made by Raytheon.  Did 
Raytheon make tubes for Eimac???

Other markings on the tube include a JAN-CBZC-8166 / 4-1000A and what 
may be date codes 65 25

Inside the tube  on the lower support structure are the numbers  523 557

Can anything be inferred from these numbers?