I tend to agree with Armadillo in that a "collector" acquires firearms primarily to fit a specific pattern, topic or theme. As opposed to an accumulator that makes more random selections based on what interests them at the time or has practical use.

There are infinite possible themes to pursue. For example, one of every variation of a particular model such as the P-35 collector mentioned. Military weapons used by all major combatants in a specific war is popular. And I suppose, NIB revolvers does constitute a theme.

I like to think I collect pre-war .32 caliber semi-auto pocket pistols. Mostly satisfied with finding one model of all major manufacturers of the era.

I accumulate S&W and Colt revolvers. Buying anything that interests me at the time and is reasonably priced.