In the May 1997 issue of Railmodel Journal, p 12, Richard Hendrickson writes “In the late 50s, in order to supply some of its leasing customers larger cars, Mather built some 50-foot cars with double doors by simply splicing two 40-foot cars together. Some of these were single-deck cars, but most were double-deck.”

Burlington Bulletin #25 was published in April 1992. It has already been cited regarding the 1952 date. Though the CB&Q did not acquire any 50’ Mather design cars until 63 (after the cutoff date of this list). Author Hol Wagner does note the 40’ cars leased by the CBQ were off lease from the B&O, and came to the CBQ from Mather/North American wearing NAHX reporting marks before being repainted by the Q in Chinese Red. But he acknowledges he did not know the heritage of the 50’ cars, simply mentioning they were identical to NKP and NYC 50’ cars.

Much has been learned since the early 90s, but it appears we are still missing the definitive date as the actual creation of the 50’ Mather design stockcar.