Assume watermark type is same as preceding stamps/sets, and Typo means Typograph print.
Placing "Typo" and no watermark no means preceding set/stamp has the same watermark, and is printed in a different way, eg "Litho".
Only differences from preceding sets/stamps are shown at the beginning of each set.
Is that clear? I'm not sure if I have conveyed my intent very well.
The introduction, index and identifiers to the catalogs provide a wealth of information regarding how to use and read the catalogs, in addition to much more.
Michael...I actually looked there first, but at the watermark section. I want back and found what I was looking for under types of paper. Lots of info, but I'll be darned if I still cannot not tell if the stamp I'm researching is Typo or Chalky. The added look did lead to something though. It is a Federated State of Malay stamp. It looks unused. However, I looked at it closer under 8x mag to see if printing was raised at all and discovered a very tiny green line and a few other green tinges that now make me think it's used. Without the magnification you cannot see it.
Boy, this stuff takes time....but damned interesting.