I put a new Id tag one every completely restored ECO I sell. Initially I tried to stamp my own, but as I explained above, it took practice. Use an old tag, start stamping, observe how apart the stamps should be, also observe how to keep the letters/numbers on the same level. This is not rocket science, it doesn't matter where you practice on the old one, it won't take you long to find out you can replicate the original.
Author, Gas Pump Identfication books 1st & 2nd Editions & Air Meter Identification books
We rebuild ECO air meters and sell parts.