Got tired of buying expensive tags so started experimenting. Tried using soda cans but the metal is way too thin. Tried folding the soda can metal so it was 4 layers thick so basically you got 2 tags from each can.....worked but labor intensive.
I settled on aluminum flashing. The stuff is thick enough that you can't tear the holes out. Like $25 at lowes though they also sell a smaller roll for $10.
Tried cutting it as is which did not work well so decided to try wrapping the flashing tightly around schedule 40 3" pvc scraps I had and that worked great.

It gave it the rigidity to cut slices with the metal bandsaw. Covered the outside in tape before I cut the slices so it would not unroll when cutting.
This is what you end up with.
You drill 4 holes throught the entire thing, North south east and west. When you unroll it you get this.
They are easily cut with ordinary scissors and the tags are strong, you can't tear tear the hole out yet easily indented with a ballpoint pen for permanent marking. Thin tie wire to attach and you are set.
Cut 1/2 wide you will get 6000 tags from the roll which is what like 40 cents per 100? The entire project start to finish took about 30 minutes and a lifetime of tags.
I realize not everyone has a metal bandsaw though I am sure there are other ways to cut the slices, all the other tools needed are common ones.