Thanks for lightening the pics for me! You can definitely see the detail better. I am new collecting Krags and the only book I have  Poyer's. He only mentions 1 prototype that was an 1892 and the Parkhurst was bolted to the receiver were as the test guns were dovetailed. Sources on the internet say they were riveted to the receiver. The screw holding it to the receiver is a standard  righty tighty.