1.  coin collection(n = noun.group) - a collection of coins;
is a kind of accumulation, aggregation, assemblage, collection

2.  coin collection(n = noun.act) coin collecting, numismatics, numismatology - the collection and study of money (and coins in particular);
is a kind of aggregation, assembling, collecting, collection

art collection, bottle collection, coin, coin bank, coin blank, coin box, coin collecting, coin collector, coin machine, coin silver, coin slot, collection, collection agent, collection plate, flip of a coin, garbage collection, loan collection, map collection, motley collection, rental collection, stamp collection, tax collection, trash collection