normally .you call one .a letterologist.
A catapultist.
onithbfdbvb
A numismatist studies the art and history of coins and coinage. Someone who just collects them is just a collector.
I would call him a hobbyist.
dumb
A button collector??
a hoarder x)
You call someone that studies metal a metallurgist.
A physicist.
Graphologist comes to mind or autograph hunter.
Those who study or collect butterflies and/or moths are called lepidopterists. The word comes from the taxonomic order to which butterflies and moths belong: Lepidoptera.
Someone with too much time on their hands and too much space?