Greetings,
From what I have been able to dig up.. The Mule Ear lock, was invented in the US and it is indeed an 1830 +/- era lock.
It seems that there is not much recorded about when and where and exactly who,,made the first one?? kind of blurr in History. Like the underhammer, I think its different appearence, had more to do with it lack of general acceptance. Most were not equiped with a half cock position,, and were generally used, if at all,,,on target rifles.
The Civil War had a Muley, that was used in limited service. The "Jenks" breechloading carbine. It loaded using loose powder and ball. the original pattent date was 1838,, and an imprved design patented in 1848. It was only the Third breech loader to be adopted by the US government.. The only one to use the side-slapper lock and also the only one to use the percussion nippple to secure the lock onto the weapon.
Dale Story, made his locks in the 1980's and it is a totaly modern design.. He was awarderd a patent for improvement to an existing design..mainly for the sear arrangement he utilized.
This picture is of My "Miss Muley" She is my takedown, back action Muke ear. I designed the lock and the takedown arrangement, myself.
That's about all I can help with!
Respect Always
Metalshaper