The year may be important

Okay, now that I have been educated that (modern) steam engine class lights did in fact have green and clear lenses in the same lantern, let me raise a different issue. Ron indicated the time frame for his picture was the 1880's. I wonder if class lights then were the same as the dual color class lights that we have discussed below. My oldest rule book is an 1908 NWP book, and unlike the more modern rule books that clearly show two lenses on class lights, the 1908 NWP book shows class lights with just a single "lens". Indeed the picture looks more like a lantern with a round globe rather than the kind of lenses in more modern class lights. The same 1908 book also carefully shows the seperate lenses on marker lights. I would opine that at least on the NWP that class lights in the early days were used a bit differently than our discussion of "modern" usage. Perhaps some pix can throw more light on this, and emphasizing an earlier note that different roads had differnet practices.
And I guess a related question might be is when did railroads start using class lights...a quick perusal of Narrow Guage in the Rockies has a few older pix with no trace of class lights.
JBW