Some very good suggestions here. Many of them crossed my mind, therefore, I have nothing getter to offer. Good luck.
I've decided to do a test and use a small dab of nail polish on the top edge of the slabs. That will allow me to: -- see what it looks like, and -- test how easy it is to remove the "dab". IF I like this then I can get various colors of nail polish that will allow me to color code the coins. That would allow me to separate my type set coins from my issue/design set coins. In other words my type set IHCs can be stored with my IHC set and I'll be able to spot them.
I suggest you test the nail polish on a slab that doesn't house one of your favorite coins. Most nail polishes contain a light-end hydrocarbon (solvent) that keeps them liquid and evaporates as it dries. This could attack the slabs plastic and cause it to cloud. Use caution.
Mine is to have as much data as possible on the coins so if they are stolen, I give the police no excuses to not do their jobs.
This inquiry reminds me of the age-old question from algebra class : If A is equal to C, and B is a part of C, then isn't B equal to A?