[Oldbayrunner]

Wonder if it possible the difference is one is the electric version which has contacts in the back that were used to communicate with the camera body to stop it down so it is slightly different without that.

[Ontarian50]

Do they look the same wide open?

Yes, that's a good way to test if the lens is properly set up, or its aperture unit has slipped inside.

I don't recall exactly how those lenses have their aperture units installed (some lenses you put together the aperture unit and then install it, rotating it to get the aperture set properly - others, the blades go right into the lens barrel and the cover plate is adjusted to set the range).

But the best way to test if one (or both) lens is not correct is to open the lens aperture up, and it should reach wide open just as the aperture ring gets to f1.8. If it's wide open earlier than that, or never reaches full wide open, then it needs adjustment.

This, of course, assumes the aperture blades are original and correct for the lens, and were properly made to operate correctly in that lens in the first place - not always a guarantee when looking at older behind-iron-curtain offerings.

And don't get me started on why aperture blades were allowed to be bright and shiny.

[Cabessius]

Do they look the same wide open?

Yes, exactly the same. No visible blades.