Thats right free, free, free,
I have a Marlin 1894p and a Winnie 1894 30-30 pre war nice gun! What I did was take out the rear sight blade tha held in with a single tiny screw, don't loose it, then make a new one from a piece of tin can lid or what ever you can find thats the same thickness. drill a 1/16 th. hole near the top of the new blade, you will need to bevel the edges with a file as the old ones were. Paint it black or blue it, sight in at 25 yds. and enjoy!!!
Or you could buy $130 Marbles, or pay bills or spend it on ammo.
Make 2 or 3 with different size holes to fit your shooting needs.
3shotz1hol4u qweeksdraw