The old copper penny was often used in the old fuse boxes if a fuse was blown. They looked bad when they were removed, if you got them out before the house burned down.
This is not a joke. People really used to do this and yes, many of those houses burned as a result. I seem to recall at least five in the greater neighborhood where I grew up.
im a master electrician and I should have save all the cents and nickels that I have pulled out of fuse boxes.. I would probably have about 100$ easy!!! The bad part... you see the damage to the coin imagine the copper bus parts in the fuse hold it self...