Ya got me, Bob, I forgot about contractions! Sometimes it was DTTL, but in general always ETTL, rigorously placing Zone Zero where not more than 2 photons/m^2 could ever hope to reach it. Except of course for low contrast fog scenes, which Ansel grudgingly admitted required a well exposed, dense negative, and enough said about that.
Of course, we tried to avoid contractions because it pretty much gummed up the lovely microcontrast and glowering shadow detail that came along for the ride with DTTR expansions. The Zone System had a strong preference for low contrast lighting. Brovia #4, cold light head, a jar full of dodging tools, and a drawer full of cut up paper boxes with holes...it was a thing of beauty! But it's all so much simpler in LR4.