Back when I lived where there was a stamp club, I'd always carry stamps like these in my scan. I would be looking to trade for stamps I was interested in. It has always amused me when other collector would try to assign a number system to describe the centering. To me these are only well centered stamps, nothing else, in addition they are all common.
Some collectors would suggest I send them off for grading, I would say something like, you want me to pay someone who will give me a such and such number grade as to the centering, when I can do this by myself for nothing?
No two collectors at the Stamp Club would agree on the number they would assign to a well centered stamp. Some times they would disagree and spend lots of time in an effort to out talk or over talk some other collector. To me this was all a waste of time, especially for common stamps. Not worth the time or effort. They are just common well centered stamps, nothing else, not worth any more well centered or off centered!