Johnbear, I'm sure you're right about the window covering the scale. The earliest lenses I have with that are the Pentax-F which date from the early '80s. Of course some lens manufacturer could have used them earlier, but it would seem to be that era, around the 1980s, when they became more commonplace.
Conan, it would appear to get interesting here. I was looking at your photo and comparing it to my lens. The auto-diaphragm lever (to the mid-left of the lens as we look at it0 in your photo is in the closed position i.e. the blades are at the f22 position - at least they are in my lens - and yet the scale is set to f2.8. When I set my lens to f2.8 the lever is at the very back of the slot.
additionally the the lever that connects with the metering linkage is at the very front of its slot (i.e in the same position as yours) when it is set at f22 (rather than the 2.8 yours is set at).
From what we have so far it would appear that the numbering on yours is the wrong way round, but everything else is the same, that is to say it would operate perfectly but when set at f22 the lens is actually operating at f2.8 (and so on through the scale - f16=f4, f11=f5.6 and f8=f8).
Anyway, here are the photos referred to above - at least they would be if I hadn't used "quick reply". I'll post this as is then use "reply" to do the photos.
Check our Yashinon DX series . They're way older, than 1980.