Depends on which Just Suspension bars they are. Originally they were zero indexed, and had no markings as to which were left and right. It didn't matter until they were installed. The later ones I think were indexed, and those should be marked left and right. If you have the older non-indexed bars, there's no way to tell them apart if you didn't mark them. Unless you can figure out which sides were which based on any witness marks or scratches from headers, steering stuff, etc.
I think the idea that they'll break if mounted on the opposite side they were previously mounted on is overblown. Spring steel doesn't work harden like regular steel, if it did it wouldn't be very useful as a spring! I definitely think best practice is to maintain them on the same side as they've been run on, but unless the bars have sagged significantly (offsetting the hexes) in their previous direction I don't know that I'd stress out about it too much.
