The following is copied from the 2002 RMD Regs:
>>>>(b) The issuer or custodian of the section 403(b) contract must keep records that
enable it to identify the pre-’87 account balance and subsequent changes as set forth
in paragraph (b) of this A-2 and provide such information upon request to the relevant
employee or beneficiaries with respect to the contract. If the issuer or custodian does
not keep such records, the entire account balance will be treated as subject to section
Since the breakout does not appear on your 1993 statement, it is possible that the plan did not track the pre 87 balance and will not recognize that balance when calculating your RMD. Hopefully, the plan can provide an explanation regarding this, so you will know exactly how the RMD has been determined. It is possible that this becomes a gray area with respect to the IRS, if you want to contest the amount the plan indicates is the correct RMD.