This Tag can be found on monosteel, san mai ,multibar forgings , annealed or hardend to help you pick the right toolsteel for the job. Invar36 in combination with 02 toolsteel ,the 36% ni content will results in a very high contrast and is not effected by tempering colors and wil hardly oxidise when forging it so beware of Mushrooming an cold shuts ! when even more contrast is desired try the tags and NI99.8%