Old steins should not be repaired- ruins their value as well.
For a while it was a custom here (may still be) to give glass-bottomed, silver-plated mugs to he winning team in amateur curling matches. These have gone to the Sally Ann, who have trouble disposing of them.
My old pewter measures are never used. The patina should not be removed.
A new glass mug is safer (and may be cleaned occasionally unless you like that old taproom floor taste).