I don't quite know who's buying the murderabilia described in Vinciguerra's article, but the history of the market for Nazi artifacts may offer a clue. That market had two kinds of buyers, anti-Semites and Jews. The anti-Semites made a fetish out of objects that encapsulated their worldview. The Jews obtained such material in the interest of analyzing them, distilling them and hopefully depriving them of their power. Zimmerman's gun may be of interest to racists. It may be of interest to black people who want to better understand the power of this banal object.
The binary doesn't quite work. There are those who collect Nazi memorabilia along with World War II American propaganda. In Tallinn in 2006, I went to a shop which sold military wear and paraphernalia, including Soviet and Nazi artifacts. I bought a 1990s Estonian military hat with the Estonian flag right on the front. No one in the States knew where it was from and that was the fun of wearing it. No, I can't believe I gave my money, even for an object that to me at the time represented democracy and a new ideal of Europe, to someone who sold Nazi paraphernalia either. I talked to the owner later by phone for a story that ran in the Baltic Times, which doesn't seem to be available online. He was an old soldier from the Soviet period and he said he didn't much care for Nazis or Communists. By selling all these objects together, the shop owner was commodifying them and divorcing them of any history. Together these objects depicted an idea of conflict, of war, of the nation-state, but they didn't allow for any value judgements one way or another. Remove any one of those objects individually from the store, place them in a private home and they become something else entirely.
I recognize that these analogies don't entirely work. There's a difference between selling material weapons that we know were used for killing people and icons of violence. But I do wonder if there's a possible buyer of Zimmerman's gun who is not a raging racist or gun nut who wants to fetishize the object, nor a civil rights or anti-violence activist who wants to divorce it of power, but a collector shockingly ignorant of its historical and moral weight.
Part of me thinks Zimmerman's gun belongs in a museum. I don't know how much educational value such a gun would have, but it may contain the aura of America's insane gun culture. Future generations may regard it with the same mixture of disgust and morbid curiosity with which we now consider overseer whips and hangman nooses.