For what it's worth, here is my restored 16B. I believe it to be the earlierr 5-band chassis in a later cabinet (slot on the peak). When I was working to un-bolt the chassis, I found other drilled holes in the bottom of the cabinet. Whether that was original and the older chassis was replaced by someone or whether it was drilled with both sets of holes at the factory is anybody's guess......I guess. Not sure which knobs belong on my chassis--mine are the hex type. I THINK the earlier chassis had the hex knobs, right Ron? I've seen some 16Bs with the other "rounder" knobs. I'm not sure what the correct term is for them.
Anyway, they are quite the radios. Fred, I think you're very lucky to have one of each of the cabinet variants.