OP, congratulations on your new family heirloom, it looks like from the setup it was originally assembled with a tang peep sight, and possible later with your Grandfather (eye sight getting poorer) he probably whiched over to a long relief scope.
It looks like a older Thompson Center scope and mount from the one photo.
I speak from experience on this, I can still use open sights, it just takes me longer to get the round sent down range.
My father had one like yours that he put together too. It came from Dixie Gun Works @ Union City, TN.
It had a hooded front sight with a insert, and adjustable tang peep sight. He did the blueing and stock work on the kitchen table. I can still remember mom fussing about the mess and smell in her kitchen.
Maybe your grandfather did the same, with your grandmother fussing too.
He would shoot Minnie Balls for deer (he never failed to get the job done), or patched round balls for squirrels (within 40-50 yards he would shoot them in the head). He would cast his own bullets and Minnie Balls, and round Balls.
He traded the rifle away for some other gun trade years later, I wished it was still in the family.
But I still have the memories of shooting it in the back yard with him, after he got finished with it, I was about 10 years old then. Plus dad is still alive and we have many more memories too, hunting, fishing, shooting, and other man stuff....
Edit - I did not see the other photos at first, maybe a long eye relief Redfield? Photo is blurry.