ok this is a first for me.. thought i had pulled twins off of every type of vehicle. guess not.... wonder how you pull off a pit if your on tracks... hummm https://goo.gl/images/K29pXk
more then possible that it had a mate on the other end, i know if the lens was blue that was probably a no go as blue on the rails indicates men at work a.k.a blue signal protection.
There is a grain co op in Terre Haute that has a Model 14 with a red lens mounted above the coupler on the rear of their SW1500 switch locomotive. My understanding is it was required by the city due to the large amount of street running they do.
CN had some MLW S-13 yard switchers outfitted for hump service, and at one point during their working lives the units had red Beacon Ray 17s on them instead of the usual railway locomotive beacon.