Can anyone ID this rifle? My father-in-law went to an auction and picked up several rifles and shotguns since I'm the favorite

.
There are no markings (no SN) on the gun other than the photo I posted. It has an octagonal barrel. The trigger must be pushed forward when the hammer is cocked, it's the only way to cock it. It looks to be somewhere around a .250 cal barrel.
Thoughts?