I have stumbled into some new trivia.
In 1972, MCA (U.S.) had dissolved some of it's record labels including Kapp, Decca, King and Uni (the label Elton was signed to). Up to this piont MCA Records did not exist in the U.S., it was only a head corporation. MCA Records was started to pick up the artists now left without a label. It turns out that Crocodile Rock (MCA 40000) was the first single and Don't Shoot Me... (MCA 2100) was the first album to be released under the newly formed MCA Records, Hence both having a plain black label. Both being the first number ones for the label.
Of course this tidbit had me fascinated!