[ARC5] Interesting, but why?

[Michael Hanz]

"Kenneth G. Gordon" wrote:
> I have several ARC-5 (actually ARA) broadcast band receivers
> here in which the portion of the nomenclature plate on the top of
> the case which is after the word "Date" has been "surgically
> removed" so that there is a small piece of the plate missing.
> Why would this have been done? Did the military do this?

The US Navy did this early in the war, especially for equipment used in
the Pacific theater.  I think the reason was fairly well explained in
one of the books on early wartime radar, though I don't have the
reference handy at the moment - I think it was in "Instruments of
Darkness".  In an interview with one of the British countermeasures
experts, it was clear they were able to glean an amazing amount of
technical intelligence from dismantling downed German equipment and
analyzing assembly techniques, technology improvements, etc., and
correlating it to date codes imprinted or even just written in pencil
inside the equipment.  You will see the date code removal most often on
earlier equipment like the RAX-1s and the like used in patrol aircraft
in the Pacific region for ELINT work - apparently they had the highest
probability of being lost in enemy territory.  I've seen a variety of
methods used, from neat milling machine plunge cutting, to drilling part
way through the tag, to using tin snips!  I don't recall ever seeing it
on AAC or AAF equipment, but that doesn't mean it didn't happen.

Best 73,
Mike