SSA may not grant MS credit if RRB has granted credit for MS during the WW II period,
09/16/1940 - 07/24/1947, or during the post-WW II period, 07/25/1947 -12/31/1956.
(See HI 00801.201 for ESRD claims exception.)
The mere creditability of MS by RRB does not preclude SSA credit since RRB will only
credit the MS if it is to the advantage of the worker for RR service months, a higher
annuity, or to credit MS not creditable by Social Security. RRB must have actually
used the MS to establish eligibility or to compute the benefit amount. Further, the
crediting of MS by RRB in only one of the two periods (WW II or post-WW II) does not
preclude SS credit in the other period.