(read how to identify your stamp below)
You have the 6¢ Lincoln from the years 1870-1882. It is fairly common
If the stamp has a grill embossed on the reverse of the stamp (shown below) click here.
If the stamp has no grill embossed on the reverse then examine the bottom left corner of the stamp.
If you see the thicker shading in the ribbons, as shown below, then click here.
If you do not see the thicker shading in the ribbon (shown below) then click here.
Normal shading inside ribbon
Lastly look at the lines that border the image. If there are only three lines, as shown below, click here.
Only three border lines
Normal four border lines
This stamp was reprinted in 1875 and it can be viewed by clicking here. These are all accounted for, and will be accompanied by a certificate.