Bill Mowrey of Texas designed and built a mule ear lock. He had a problem with the angle of the sear, IIRC. My friend Ken has a couple of Bill's locks, and the molds for them. I've tried to get him to let me take the moulds to a foundry, or buy them out right. Nothing doing.
I could be mistaken, but the lock Satwel has looks like Bill's, and his didn't have a half cock.
I'll try to get pics and measurements.