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 F7A 165A, F3B 165B, and F3A 165C. The train is the early morning "Pick Up" at Milledgeville, IL (122 miles from Chicago on the Twin Cities Line). If the train had a number, it was never used on the dispatcher's line. It could run 80 cars long. Yes it was a heck of a train to be doing local switching, but it did weekdays.