I bought a state-of-the-art IBM Selectric in 1975, equipped with the 'works', and it didn't have the superscript 'th' as shown in the documents Dan Rather/CBS presented last night! I am almost sure this is a big, big fake!
They presented it tonight too. It was a Kerry campaign commercial disguised (barely) as news.
The IBM Selectric did; however, have interchangeable fonts that clipped into place. You could get special character fonts, but I am not sure whether the special characters included super and subscripts.