I've bought some stuff from Paul Z; great guy and very accessible but busy running that Delphi Triumph forum along with moderating the vintage group at rat.net. My favorite reply (from across the pond) over at the rat.net was this:

"It would appear that they were applied by the guys in the factory in a pretty hap hazard fashion, so seem to vary a lot. Good luck!"

A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort. Herm Albright (1876 - 1944)