I've seen the tapered square posts referred to as "carriage keys", as in a horse and carriage. Not sure what part of the carriage they actually used them on though. (I'm quite certain it is not a doorknob tool, as the seller suggests) The Brevete and Depose markings on French-made items can be loosely translated as "Patent Pending."
I've not seen musket tools with a shaft like that, only flat versions. That said I don't go around looking at muskets so what do I know I like the tea break saving theory It does make sense though Irritatingly it also reminds me I've got to fix the lock on the bathroom door, boring