The Cover of the Jan/Feb 1970 Digital PDP11 sales brochure.
There is a popular misconception that the PDP11/20 was the first PDP 11 and that the 11/10 was introduced later, with the 11/05 and 11/40. In fact, there was a little-known "rev 1" PDP11/10 and this model was sold simultaneously with the 11/20 when the PDP11 product line was introduced in 1969. This first PDP11/10 was a turnkey unit that could be used as a process control system. A few years later a "rev 2" 11/10 was produced, this time more or less interchangeable with the new PDP11/05. This is the 11/10 most of us know.