Postal Letter

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

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.

Public Comments

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