10 Gauge Under Lifter Hammer Gun Internals

[CW Nickle]

Here are some photos for you, my serial number is 7987 which should put it in late 1876, as you can see my left hammer doesnt engage the half-cock notch too and I was curious as how to approach fixing the action for proper function. For grade markings from what I understand is that a T would designate a grade 0 gun but its not where it is supposed to be. All the serial numbers do match and are in the proper locations.