Summary

Identification ear tags have always been a problem. If you use blank tags and write with an ear tag pen, they fade and become unreadable. I you use commercially printed, (ink, not 3d) tags, you need to order a lot of tags, they are expensive and if you lose one you cannot replace it with the same number.

12 months ago I tried my first 3d printed ear tags and so far have had 100% success.

They are printed from TPU and are extremely durable, easy to read and can be printed as required. They work out a lot cheaper too.

You can change colours for year, sex, paddock identification.

They fit the standard ear tag applicator gun.
https://www.fmb.com.au/leader-applicator-standard-deluxe.html

The male part needs to be purchased separately as you would normally do for commercial ear tags.
https://www.fmb.com.au/button-male-plain-no-printing.html

To customize your own tags, copy this workspace in Onshape and edit the text and size as required.
https://cad.onshape.com/documents/5863832aeed541b703b8579a/w/a5c30d8d412f17253335b119/e/c1d6dfc8dbf670c13c504623

Here is a screencast I made to assist you in editing the text. https://youtu.be/BBkoqZsQ8L4