regardless of when uses for what was originally a waste material known as vinyl were first investigated, tape used anywhere before 1948 wasn't vinyl:
see history 1/2 way down - as noted, the earliest vinyl tape was yellow, and having seen an awful lot of vehicle wiring from 1937 onwards, I've never seen any w/ yellow [or white] tape on the wiring - as I said, I've never seen any right up to the TF years that didn't use something quite like friction tape if it didn't have cloth loom - same as my 57's and 58 had originally
you might inquire at one of the repro harness makers, who seem to use laquered cloth covered wires and braided cloth loom on the 30's & 40's harnesses that are supposed to be "as original", and modern plastic tape over the same laquered cloth wires on the 50's things
if you find other material was used at the factory, I'm sure we'd all like to hear about it
Bill
