[Hallicrafters] RCAF tube in SX-28

[Ron Gerut]

Hello:
Recently, I was working on an SX-28 and noticed one of the tubes had the
name RCAF on the label.  Does anyone know if this is a variation of
Radio Corporation of America-- or is it possible that the metal type
tube was associated with the Royal Canadian Air Force?  Considering the
WWII history of these radios, I am unsure what this could mean.
Thanks,
RON  K9KLT