Hello Christian,
I'm the last person to ask that of on this forum my friend :) I wish I had enough knowledge to help, but others here have that gift & share it ;) & their time too.
I'm in the same boat as you, I ended up with a pile of damp damaged albums a few years back on top of what I already had, & my quest started then to save them. I'm learning as I go with help from many people here, & old threads & links they have posted on the forum in the past.
Everything I wrote above I have found & learnt here searching, while sorting though a couple of hundred of my German stamps.
The value/"devil is in the detail" on stamps, you saw the Mexican thread of mine, those are one of the types of stamps you are looking for if it's added value you hunt, there are many variations. Any little differences from the normal ones ;) are good.
It takes lots of time but bets watching TV.
I haven't even started on learning the Aussie ones yet ;)
You have a steep learning curve coming on the search function, but I'm sure you will enjoy the history that many here share in their threads.
All the best with your quest, later......Jad
This will get you started......check out the links in the threads you find ;)
https://goscf.com/t/13085Here are both possible watermarks for your 30pf, note the huge difference in values, these & other seemly small differences are what you are looking to check on stamps.
http://www.philadb.com/?site=list&c...=484&id=2272http://www.philadb.com/?site=list&c...d=484&id=875Good luck !