Tom- C75 is a 20 cents denomination and the C81 is a 21 cents denomination. Same design- different colors and denominations.
Thank you John, I feel very silly for not seeing this. Tom C. (red faced)
Don't feel badly. Sometimes catalogue listings can be a bit cryptic. It's called "catalogue blindness" in dealer circles. It is sort of like the old saw "I can't see the forest for the trees". We all suffer from it at one time or another! David