Winchester made a single they called a "Semi-Hammerless" I believe. It was the model 37 & was striker fired & had a cocking piece which set low to the tang. This piece was attached to the rear of the striker so it was actually hammerless, though required hand cocking.
I have an old Remington single with internal hammer but is not self cocking. This one uses a side lever for cocking, so no visable hammer.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra