US Instrument/Part Numbering Convention Evolution

[2banaviator]

For Parts Specialists who may be as "anally-retentive" as I've become on the subject:

I've looked at identification numbers on aircraft instruments for a few years now, have deduced some findings, but would love to find some definitive info.
I'm trying to piece together the evolution of the part numbering systems used by the ACUSArmy, AFUSArmy, US Navy, and USAF, from 1940-1960s.

Herewith:

Up to 1943 (based upon a review of the "Maintenance Interchangeability Cross Reference Charts of the US Army Air Forces dated Dec 1943 (TO 00-25-29)", the numbering system appears to be evolving from strict manufacturing part numbers to US Govt Type numbers, and AN (Army/Navy) numbers. Appears to be an equal distribution assigned to parts, where some only have manuf (Vendor) part numbers, some also with Type numbers, some with manuf part numbers but with AN numbers instead of Type numbers.

Now here comes a document "Index of Army Aeronautical Equipment (with Navy and British Equivalents), Vol 6 Instruments dated March 1944". Type numbers referenced extensively, as are AN numbers. "F.S.S.C." numbers begin appearing for some instruments (both on the instrument and in this document), but no explanation is provided as to its use in terms of identification or procurement purposes.

As I've perused manuals from US military aircraft of the later 1940's-early-1950's, a divergence becomes evident in the numbering system used by USN and USAF aircraft. USN instruments are more frequently marked with "R88" prefixed-FSSC numbers and correlated with other USN markings (e.g. USN anchor symbol or BU AERO USN) than others.

USAF of the 1950's seem to move toward the MIL spec system. Seems to become even more complicated. The only way I've found to determine if an instrument was use in an aircraft of one service or the other is to identify any in-service labels associated with the instrument, e.g ., NAS San Diego or OCAMA)
Then we have the "Stock Number" that seems to have entered in the 1960s.

Ultimately, I trying to determine: if an instrument's label has information "X', then it is probably from time period "Y", from military branch "Z', and perhaps used in aircraft "Q". An ambitious exercise to be sure. Either Help or Sympathy is acceptable at this point.

Anyone who would like to peruse the aforementioned documents, either email me or or search my prior posts.

JT

[Taigh Ramey]

I have wondered about this as well. Interesting what the differences were for the Army and Navy throughout the war. I am under the impression that the 88 is Navy and 94 was Army but that is based on speculation and observances. In researching the instrumentation for our PV-2 all of the instruments listed in the parts manual and the drawings use R88 numbers.

My Index of Aeronautical Equipment, Instruments is dated at revised in March of 1944 and it shows quite a lot of AN and Army designation equivalents.

I would love to learn more.