3M M-131

3M, the same company that makes well-known everyday products such as Scotch tape, entered the traffic control industry in 1969 with High-Visibility signals. These lights were unlike any other at the time in both design and operation. They featured PAR-46 lamps in the back of the signal, with an opening back housing that had an auto-disconnect to prevent electrical shock. This light would shine through multiple layers, which helped prevent a condition known as the 'sun phantom effect', where a signal would appear to be lit in all 3 indications during sunrise or sunset. The unique signal build also offered 'programmable visibility', where a technician could mask off parts of the road the signal faced so only certain lanes or areas saw the signal indication, while masked off areas saw the signal as off or very very dimly lit. At a time before louvers, this was very helpful in congested or crammed areas where drivers could be confused or overwhelmed by the number of signals lit. This unique feature came at it's own cost, however. A 3-section M-131, the most common model, weighs in at around 65 pounds, whereas the average 3-section 12" head comes in at around 40 pounds. Also, as mentioned, the M-131 uses PAR-46 lamps, which have much shorter lives than the average signal bulbs, and cost considerably more each. The PAR-46 bulbs also get incredibly hot after being on for a while, which is an inconvenience for collectors and field technicians. McCain produces a near-identical line of High-Visiblity Signals as well, which are understood to cost less but weigh around 80 pounds per 3-section head. 3M stopped producing this line in 2007, due to decreasing orders. Many collectors like to have at least one of these signals due to their unusual design. This M-131 came from a forum member in Ohio, and arrived with faded paint but in great shape otherwise. It received a layer of ACE School Bus Yellow shortly after reassembly.