1451 A Or B National Parks 100

Is this a 1451 A or B National Parks 100 stamp. It does have a nice cancel.

That is 1451a, as 1451b has the black omitted (U.S. 2c etc) in error.

The block is one of my all-time favourites of US se-tennants.

It's a 1451a (note small "a"). 1451b would be an block with the black print omitted (in error) and would be worth thousands. The cancellation is nice, but was very common during the period these stamps were in use.

Thank you, the software I am using had "black (litho.) omitted" but still showed the stamp with black in it.

bad software, bad!

you will find that all the software will use the original image for an error when they don't have the correct one.
as the images must all be scans of stamps they own or images that have been given to them by the people who own stamps.. This is simply a copyright law issue.

I have sent numerous images of pre-1900 stamped envelope pictures from all the different varieties I collect to the guy who I bought the software from. That's one of the things to look for when buying software.. how many images they have for your country of interest and how many total for the world..