I notice some Checker cabs have been renamed as Taxicab instead of Marathon. What's the difference?

There are A9, A11 & A12 models, the A12 being the Marathon. I think that the A9/A11 is older and a little less "fancy", being taxi-only (though that the A12 was probably sold mostly as taxi)
http://www.imcdb.org/yourcomments.php?id=superba