(read how to identify your stamp below)
You will notice the stamp to the left tends to be more of a carmine color than the stamp on the right. If the stamp does not have an embossed grill (shown below) and errs towards the carmine of the left stamp then click here.
If the stamps color errs towards the carmine of the stamp on the left and has an embossed grill (an example is shown above) click here.
If the stamp tends towards the rose-carmine of the stamp on the right then click here or here. The latter stamp is printed on a softer porous paper and if it has a reconisable date on a postmark it will be after Feb. 4th 1879
This stamp was reprinted (Scott #177) in a violet carmine color in 1875 and it can be viewed by clicking here. These are all accounted for, and will be accompanied by a certificate.
The stamps color was changed to purple in 1888. Click here for details