Agreeing with replies +10 in mainstream context of "serious collector". Expanding that to "X" as representing about anything of value accumulated in big bucks context.
My question back, "What's it to you?" Perhaps if you expand, some such type to reach out to you. IF simply guns for sale and to "cut out middle man", those persons also playing important role beyond just hooking buyers & sellers.
Point to ponder!
Best & Stay Safe
John
