Don't call a coin collector a philatelist. That word is reserved for people who collect stamps. If you're going to become a philatelist, start saving those old envelopes.
The phil- at the beginning of philatelist gives you a hint as to its meaning: it means "love" — a Francophile is a person who loves France. The Greek ateleia meant "exemption from payment," an exemption that was marked by a stamp. So a philatelist is literally a person who "loves stamps." The world of the philatelist is a strange and tiny one. It makes one wonder why someone starts collecting stamps in the first place. Maybe it's the pretty little pictures.