One use I’ve heard of for bearer bonds is as a way to earn interest on all that cash you’re stuffing into your mattress.
In other words, if you want to have a lot of money hidden in your residence (or where-ever) for whatever reason, one way to do it is to stuff your mattress with cash. But this won’t earn interest. So instead, you might use bearer bonds, and keep them with your guns, ammo, and cigarettes for barter when the great breakdown comes
By the way, I think that bearer bonds, by their very nature, are negotiable instruments. Thus, the phrase “negotiable bearer bond” would seem redundant.