never heard of a 120mm, sounds like a bit of an oddity.
Pentex made 42mm lens from 35mm to 150, for the most part, in 15mm increments, although from some reason they jumped to 105 rather than 100: 35, 50, 85, 105, 120 135, and 150. The 120 is somewhat rare, the 150 is easy to find.
Good morning, Paul;
The "15 mm increment" lilsting has some other anomalies in addition to the 105 mm. The 50 mm to 85 mm is another.
There seems to be many curiousities in the way lenses were chosen.
Ralph Javins, Latte Land, Washington
When they ask you; "How many Mega Pixels you got in your camera?"
just tell them; "I use activated silver bromide crystals tor my image storage media."