Yep, Struck Through Grease, the crevases (remember the devices are reversed image) of the die get filled up with residue from polishing (diamond polish/lubricant), dust, dirt, etc. Note on this diagram from Coop:
Disclaimer: While a tremendous amount of effort goes into ensuring the accuracy of the information contained in this site, Coin Community assumes no liability for errors. Copyright 2005 - 2026 Coin Community Family- all rights reserved worldwide. Use of any images or content on this website without prior written permission of Coin Community or the original lender is strictly prohibited. Contact Us | Advertise Here | Privacy Policy / Terms of Use