http://www.teknatool.com/products/Lathe ... r_page.htm
If you look at this list, it doesn't look like the insert letters correlate to anything other than they ran out of numbers and went to the alphabet.
http://godissemperfidelis.com/Shopsmith ... _small.jpg
If you read the Nova letter on the link above, it seems that anyone who was provided a F-type adapter was complimentary provided an S-type adapter which will "ensure the best possible fit, chuck accuracy, and safety." The word safety always draws my attention. I know Dusty was missed, but he has the S-type adapter now after a phone call. This entire thread began about an accuracy or run out issue- interesting. I thought this thread had sort of migrated off subject, but it hasn't according to the Nova letter as it addresses accuracy.
I click on US dealers and there are a number except Shopsmith isn't on the list as a Nova dealer. But then Shopsmith sells the Shopsmith or products of other companies made to Shopsmith specs like the Incra products and the newest is Teknatool, I believe. Teknatool also manufactures the DVR motor used in the Shopsmith PowerPro upgrade & it has really made the Shopsmith a more powerful & energy efficient woodworking tool which was essentially a cut and paste from one good tool to another to create something better. I think that is called synergy.
I note the letter has the old Teknatool address in Florida whereas the new catalog reflects the new address on 34th Street. The new catalog makes no mention of the F-type adapter yet they are some still floating out there and people like myself a couple of weeks ago got one even after I specified an adapter for a Shopsmith. I'm confident it will be all sorted out.
I looked through the web site and found something really cool one of the other members had mentioned to me: the Teknatool Ornamental Turner which shows sold out status.
http://www.teknatool.com/products/Speci ... mental.htm
What a cool tool, but I do not believe it was ever adapted for the Shopsmith. The only thing close to it I've ever seen is a pic Bill Mayo posted of his Brownie he modified as a machine lathe. I would love to have something like that sits on the way tubes and permits simple machining operations. But first I want to start turning some wood.
Retired Air Force, BTW.

But for all of us who served, we're all brothers.