Socrativestor:

:

If one hold TIAA Tradiational in an IRA and later converts some/all of that IRA to a Roth, are the original vintages preserved or is the conversion treated as a sale in the IRA and a new purchase in the Roth?

If you have traditional in an SRA or IRA, then there would be no change in vintages by converting your SRA or IRA to a Roth.

If you have traditional in a RA, then there would be an extra step in the process by using a TPA to move 10% per year into the present vintage of a SRA.... ,thus changing your vintage structure.  

However, do confirm this with T/C before making any of these changes

Dick.