By "large scale" I meant something used by, well, a lot of people. More than a university's CS department (or the math or EE department; whichever side had the proto-CS faculty in 1975). Like, V6 was being used across Bell Labs, but I wouldn't call that a large-scale deployment compared to MTS, let alone DTSS. When V6 was ported to IBM mainframes by Eric Schmidt and others, that didn't result in Unix being made available to any Princeton student who wanted an account. Nor did the Interdata port result in a campuswide Unix system for all Wollongong students. In both cases, had a random student wanted a computer account and was eligible for one, he would have received something on a batch system.