In the early times, pigeons where stamped in their wing with some marks like the hometown place of the club and a stamp with the release location and a number, when the pigeon came back, the officials noted the wing marks on a paper before they handle the clock for registrating the time.

Het Handelsblad 26-08-1876 Ed.1 p.2

These type of clocks had no drum like the younger pigeon clocks for dropping in the rubber rings. Some younger clocks have a writing space often when several racers use the same clock.