Does any one know if metal powder flasks existed in the 1750-1800 era? All I ever see are horns until the 1850s or so.

I've seen photos of cased flint dueling pistols with a copper flask in its own compartment. Also found a picture on an antique site of a late 18th/early 19th century metal flask. I think they existed, but may have been more often used by rich folk and were generally rather rare. Do a search on '18th century powder flask' and you'll likely hit some antique sites with pictures of flasks with metal, horn or leather bodies.