Early F units usually came in set of 4, i.e., ABBA. The CB&Q found that for most trains on its mostly flat railroad ABA sets were sufficient so the ABBAs were broken into ABs with another newer A added. On the CB&Q an ABBA set was lettered ABCD and an ABA set was lettered ABC. In this picture we see CB&Q 165A, an F7A and 165B and C, F3B and A. Is this the A end or the C end?
