Reply #17: It also could have been an IBM Executive, which was capable

[amandabeech]

of proportionate spacing, and may have had the superscript "th" available as a key variation. It did not have the "golf ball" typing element, but instead the regular keys. Someone on one of the other threads stated that he/she sold these things back in the '60s and '70s and was familiar with them.

The regular Selectrics, I, II and Correcting, didn't have the proportionate spacing, but their was a special Selectric which could. They were not that common. The IBM Executive was far more common in that era, apparently.