How can I find proper sale prices of old but rare used and unused postal stamps from various countries ?

Question

I am having a huge collection of used and unused postal stamps (approximately more than 10000 postal stamps) from various countries (more than 80 countries). I assume that some of them may be very rare. But I don't know which postal stamp is rare and what could be its' sale price. I have sorted some stamps countrywise and still more then 8000 stamps are lying unorganised manner. Please guide me in easier way of sorting them as well as selling them.

Answer 1

Coin dealers would have the books in there stores you could browse through.