Thank you really much for your kind comments. Posting a comment again on that thread is like putting an old philatelic ghost alive for me. Philatelically, I changed and learned so much in only a few months that my knowledge is almost ridiculous comparated to now.
I learned that cash value is not really important in philately, (except when you buy them, of course) but philatelic value is way more important. I think this thread was one of the most important in my philatelic learning travelling and was necessary to exist.
Thank you for the advice about Ebay auctions, will take a look at that.

I think at 18 years old, seriously collecting stamps is out of the ordinary too! Really impressive.
