I read a recommendation (here?) to put coiled wire into an empty
"tin" can for more even heating while annealing. So, I emptied a tin
can and now find that it has a coating inside. I assume it’s some
sort of polymer, but it doesn’t scrap off or burn off easily.
I use a small tin that watchmakers use to store parts and stuff. It
measures approximately 1 1/2" in diameter and 3/4" high. I have had
it for many years and it works great.
Good luck and take care,