Hi,
Having read the thread through I'm beginning to appreciate, fully, the APS cameras. And they number the cartridges.
BTW, when taking two cameras with the same film in but different lenses, usual for a show, I usually photograph on of the cameras at the start to identify both of them on the film. It wastes a frame but then I often get 38 to a cassette.
Some time ago, for all these reminders etc, I thought that a blackboard and a piece of chalk would be an improvement. I bought one a few years ago and screwed it to the wall; haven't looked back since then (and no batteries required).
Regards, David