There seem to be a number of forensic document experts who, on initial review of non-original documents, are skeptical of the source documents' authenticity. Far as I know, CBS has not named their vetting experts and none have come forward. Original documents have not been made available, either. Daily Kos has made the case that the typography of the copies published "could" have been produced with typewriters in 1973, based on claims by third parties that it was possible, but that doesn't prove they are genuine, as even they admit. Maybe someone from IBM will make some official clarification of what their machines could or couldn't do then. Given that the machines which are claimed to have been capable of such typography were considered "very" expensive at the time, the likelihood of TANG having one would seem remote. I routinely used an IBM Selectric up through 1971 and it didn't have the ability to do superscripts. When I was in the Navy from 1978 through 1980, IBM Selectrics were common, but in looking through my Navy records (still have them, don't ask me why) I could find no superscripts anywhere, even where nomials were used.
I'm willing to let this play out further, but my money is still on them being bogus.
Cheers,
Daiwa