With MF cameras that have a reminder window, I often put a piece of the wrapper that says the film type in the reminder. It's not as slick as a box tab, but then on Kodak and Fuji anymore you only get one tab on the box of 5(and I rarely carry full boxes around anymore). I miss the old Fuji 20 roll boxes that had several tabs you could tear off-they did that for both 35mm and 120 20-roll boxes.
At least on Hasselblad "A" backs, the reminder window springs out in such a way that you can tuck the little piece of mylar back there easily. I also miss Kodak printing the film type on paper tab at the start of the roll, as that was really easy to tuck in and keep track of.
I have a couple of the original Hasselblad "12" type backs that I still use. At least on those too with MOST film if I really forget, I can open the peephole and watch while I slowly advance, as most films do at least still print the stock between frame numbers on the backing paper.
I've opened LF holders with unknown film in the dark before to check the notch codes, although on a few occasions I've been stumped on what I found. If I loaded them myself, chances are I know the possibilities for what's there(especially since now I think the only stock I have is FP4+, TXP-320, and RVP). When I was buying used holders, I got in the habit of checking them in the dark as I got some "freebie" film to play around with that way, but there again I had more than a few that stumped me. There are a few online resources for notch codes(IIRC University of Louisville libraries had a pretty comprehensive one...) but I found a few that I couldn't find in any of those resources.