20 CFR §404.1412

As used in this subpart, a compensation quarter of coverage is any quarter of coverage computed with respect to compensation paid to an individual for railroad employment after 1936 and prior to 1975 in accordance with the provisions for determining such quarters of coverage as contained in section 5(l)(4) of the Railroad Retirement Act of 1937. (For years beginning 1975, see § 404.1410(b)).