Northerner said:
Retro sign wins the prize!
Ah but now we have to guess what the sign says so...
It has to be a long worded sign like
Supercalifragilisticexpialidocious but this isn't 'boombox related' so I'll go for
National Panasonic. Mind you, I suppose it may be a jovial sign saying something akin to "
Roll up, roll up, getcha boomboxes 'ere" or even a sign saying 'WARNING - Boomboxes In Transit' for your Boom Bus? .