A flintlock is an old type of gun which requires the spark from a flint to fire.  It can also mean the device used to produce that spark.

There were flintlock rifles as well as much larger guns which could fire shots weighing up to 32 lb on board HMS Victory during the Battle of Trafalgar.

I didn’t get to keep any description of gun (nor that hat, sadly) but I do have the jacket and a piece of flint just like those which would have been used in a flintlock.