You have the 30c Hamilton from the years 1870-1882. It is fairly uncommon.

BLACK STAMPS

If the stamp errs towards the black of the stamp on the upper left and has no grill embossed on the stamp (an example grill is shown below) then click on the numbers 145-155 on the menu to the left.

If the stamp errs towards the black of the stamp on the upper left and has an embossed grill pattern on the stamp (an example is shown below), then click on the numbers 134-144 on the menu to the left.

If the stamp is even more black than the stamp on the upper left, has no grill, and feels like it is printed on soft porous paper, click on the numbers 182-191 on the menu to the left

GREY-BLACK STAMPS

If, on the other hand, the stamp tends towards the gray tones of the stamp above right then click on the numbers 156-166 on the menu to the left.

Example of a grill

This stamp was reprinted in 1875 and it can be viewed by clicking on the numbers 167-177. These are all accounted for, so you will not own this.

The stamps color was changed to brown in 1888. The brown version can be found by clicking the numbers 215-218 on the menu to the left.