Sorting 30-06 brass today came across 20 empties of CAC.

Looks like it's "

Colonial Ammunition Co., Footscray, Australia

CAC brand was widely sold here in New Zealand for many years up to maybe the early '80s. Used to be my main brand in .303 and .308
I kept a lot of empty brass. When I got interested in handloading I used this brass but found the failure rate pretty high. Have seen comments over the years that the brass was not of high quality.
You are correct, CAC = Colonial Ammunition Company
I seem to remember being told much of this ammo was Canadian manufactured ... ??