Rottenstone
Rottenstone was used by soldiers to help maintain their weapons. They would dip a cloth into a little water or oil, then add some rottenstone powder out of the tin and rub down the metal
on their musket. Made from finely ground limestone, rottenstone is a gentle abrasive that will take surface rust off a musket's barrel and lockplates. If you need to purchase some
check out this link: https://comersgunworks.com/shop/ols/products/rottenstone