For anyone still curious, I posted a copy of the original query on the 140/160 forum. Someone responded that Brembo's site includes a search function of their catalog by dimensions. Thus, this afternoon, with the wind howling, I have one of the offending steel donuts on my desk. Here's what I've learned: All 240 discs are 263mm diameter, thus I've left that column out. Also, only vented apps listed. All of this is 240.

Year****Disc Thickness****Overall Thickness****Brembo #****Caliper Type
To 7/75********24****************64.3***************25226*********ATE
To 7/75********22****************67.3***************25242*********Girling
8/75-87********22****************67.3***************25242*********No Spec
88-93**********22****************67.3***************25242*********No Spec

Here are my conclusions: First, "No Spec", I must assume that only Girling was available, and this appears to be for all of North America including Canada. I'm willing to buy that. In twenty years of junkyarding for 240s, I've yet to find ATE front calipers. A few months ago I stumbled on a '75 245, but did not look at brakes.

3mm of extra total thickness (67.3) and the lessened disc thickness (22) equates to 1.783" in hat height--which is what a couple of us measure on our later cars. I have no explanation for the one poster's short hat height on a later car--that's a puzzler.

My rotors are for 1975 ATE cars. Looks like only the Bertones may have had these as they came with vented discs. Curses on the E-bay vendor and shame on me for not having checked more carefully before buying!

DS