Hello Gary,
Bruce Hansen published the Erector Parts Guide from 1933 to 1962. I don’t believe he published one for earlier parts. I have an Erector Parts illustrated guide of which I have no idea who published it. (See photo below.) As I recall, it was purchased on ebay.
That guide list all or most parts, but is not very detailed. The illustration of parts, I believe, is taken from the manuals. The index for the parts list a 2 digit year at the end of the part listing (See photo below.), which I think is the first year that part appeared.
Of course you can always go to the parts list in the manual to identify parts as well.
I hope that helps a bit.