315 is fortunate enough to have a correct set of these VERY Rare lamps. Needless to say, we never let them out of our sight, They even sleep with us in our rooms when we are on excursions. We also take very good care of them.
There are two lenses inside each lamp. Clear, and Green. Inside there is a rotating metal shield to block one of the lenses so you could choose either Green or White. The mounting bracket had a tighter ring that held the lantern, and let you rotate in the bracket to allow placement of either the clear, or green lens forward. These were originally kerosene, and when the D&RGW converted them to elect. The shops simply removed the top half of the lantern, made a sheet metal cover that had the elect connection come thru the new cover, and the bulb simply hangs from the cover, These were the flat top ones you can see without the chimneys.
Yes, the lenses were on the fresnel, design. I don't know if these lenses were originally pressed just for these lanterns, of if they were off the shelf marine lenses. I have seen a number of marine lanterns that appear to have very similar lenses.