Classical fonts are designed following optical rules, which makes them indeed slightly different in size at the same print size. Some characters go below "zero" or end above "top". Making all characters exactly the same absolute size, would make a text looking optically unequal. At 10 the zero IS taller than one.
The white dial Portugese Perpetual is designed for its optical appearance : You cannot put the 8 on the same line as 4, because 8 would touch the year window. Putting the 4 higher leaves a hole between the minuterie and the 4. Same for 7 and 5.
You should not look at one single element, but at the dial as one element. The numbers you compare are "far away" from eachother. So it is more important to adjust the 8 with elements close to it - same for the others. your eyes are not jumping from one to the other side, but do follow the minuterie.
This message has been edited by magellan on 2009-10-11 11:00:43