Thank you very much!
That explains why I could not see Form 8606 for 1985. But I got a Form 5498 in 1985 from Vanguard showing contributions to IRA for that year and with the corresponding market value at end of the year. In 1988, I also got Form 5498, no contribution but with market value of the account at end of the year. Any thoughts then as to whether the 1985 contribution should form part of the cost basis?