Having been a member of both an offroad race club and a boating club that does displays with other clubs out of town, both clubs adopted a 'pin-board' system which was basically a set of clothes-pins, each having a frequency of one of the surface channels on it. When you went to operate, you checked the board, and if your frequency pin was there, you took it and clipped it to your antenna. If it was taken already, you changed frequencies, or waited. Makes sense, right?

Someone paid to have it upgraded, with better clips, plastic-etched freq tags attached to 'em, and a neatly done board to match.

An easy way to do it now would be to use those clip=on badge=tags for conventions, and just print the freq's on each tag, and the badge clips onto the antenna or radio somewhere.

Easy-peasy, right?