Something caught my attention when this showed up on my screen: the brake levers on the bike on the left. It's 1938 and these guys finished first and second in a criterium race in Rotterdam. The man on the left is Gerrit van der Ruit, and he came in second with just a front brake on his bike.
I looked him up and found another pic that confirmed that this was not a coincidence:
Gerrit was a professional rider from 1933 to 1939 and rode for Dosche Sport most of his career. BTW, the man on the right is Jan Gommers, the winner of the race.