3M M-131-375(Y)

I sold my first 3M signal after growing bored of it, only to change my mind quite soon after. A seller in New Jersey had a large number of 3M signals in his back yard, which was quite the experience to see for myself! The signal I chose had a red ball, a yellow ball, and a green arrow, so I elected to swap the yellow ball with a yellow arrow, with his permission. I later acquired a red arrow lens on Ebay, new old stock.