Old40rod,
The Mule ear lock is considered to be a mid to late 1830's era lock. It was used infrequently up and through the 1850's. After the start of the 1860's and the Civil war, it pretty much fell by the wayside.
The CW Jenks carbine,< although a breech loader, using loose powder and ball> had its original patent approved in something like 1837-38. A later improved patent was issued in 1849. This was the only gun adapted by the US military to utilize a mule ear lock. The only one who had its lockplate held onto the weapon by it percussion cone. and only the third US model to load from the wrong end.
:{D
There was a Maynard tape primed variant produced. and it's lineage continued on with the Merril carbine, which is considered an improved Jenks.
Hope this helps some..
and yes, I kinda like the Jenks carbines. So much so, I'm trying to buld one from scratch..
Respect Always
Metalshaper