Yes, as long as the plan tracks your 12/31/86 balance, that portion of your total balance is not subject to RMDs until age 75. If you have a plan statement from any prior year after 1986, it should show your 12/31/86 balance. If you ever took a distribution from the plan since that time, the distribution would come from your old balance first, so if you find a statement dated prior to the year you took a distribution, then that old balance would be less now. So look for a statement that is after the latest distribution you took (if any). If after taking your RMD you roll the rest over to an IRA, your IRA RMDs must be based on the total IRA balance since the age 75 exemption only applies to RMDs for the 403b plan itself.