[R-390] Weird 26Z5W variant??

[Llgpt at aol.com]

Interesting, as I have "NEVER" seen any 26Z5W's that weren't Tung Sols.  
Possibly used in the R-648? Not sure if they used 26Z5W's or not.
 
Les Locklear
 
 
In a message dated 2/10/2005 8:38:29 PM Central Standard Time,  
gkaufman at the-planet.org writes:

It looks  like Bendix made a hardened version of the 26Z5W  numbered
RXB-103379.

Ok, don't laugh at my bid, but I grabbed a pair  off of  Ebay:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5748382448

Anyone  ever see these before, or know why the military needed a  hardened
variant?

Were these ever used in R390A's?

- Gary  KB1FBI