Here is a little tip that I have been using and it may be helpful to others.
I use a label maker for my equipment for a lot of things because it doesn't mar the finish, and it is neat.
I can label +/- signs for battery compartments that are poorly labeled (pocket wizards etc).
Here is a really cool one. For my 400mm 5.6 l tele, I find that the AFMA for close in work has a different adjustment compared to far away. I calibrated it and I put the figure on the lens hood, so I can quickly change it out as needed. The label is easily changed as calibration changes.
Obviously, not a permanent identification, but that is the point.
I hope this is helpful, and I would be interested if anyone else uses this and if so, there are other uses for it.