This lens has the number 9074 molded in it.  The red version of this lens is mounted in two of three openings in the three-light array on the back corners of Airstreams starting in 1975 (some 1974 models). It was used for many, many years in the Airstream and Argosy two-, three-, and four-light arrays.  

Also used on Boles trailers starting in mid-60s through to the end of production and on Avions in the early 1980s.  Even some Goshen Coach buses use it.

The amber version is offered to assist our European customers who want to modify their trailers for European standards.

It mounts with four screws (not included).  Screws are 3-5/8" apart. Overall size is 4.3" x 4.3"