What is the value of a Browing Sweet Sixteen in good condition with a misprint on the barrel States use only 2 34 12 gauge shells?

I'm surprised about a barrel being mis-stamped. That could be a liability for FN/Browning. Please dissasemble with the barrel off the gun and double check that the barrel actually is a 16ga chamber. Check to be sure a 12ga shell will not fit. As far as the value of the gun, more information is needed to determine an estimation of value such as date of mfg (serial number) Condition such as "does it have a pad, or choking device?"; % of finish and more. I don't believe the misprinted barrel would do much to the value (either increase or decrease value). To a collector it would simply be an oddity or curio. As a gun to be used, or handed down in the family, it would need to be told over and over not to load a 12ga shell into it. This could be a danger and cause harm if an inexperienced person ends up with it. I would recommend sending it to Browning for replacement or correcting the markings. It won't lose any value to the gun, other than a story to talk about in the duck blind.