Your caption with the illustration calls it a "turn top" lamp. That would seem to indicate that something turns, likely the entire top, bail, and an inner sleeve that carries the green lenses. If so, there needs to be a detent that keeps it in place, and I go with the spring plunger idea.

On Edit:

Here is a patent for movable lenses in a Peter Gray lamp, but doesn't seem to key with the "turn top" name:

https://www.google.com/patents/US106222 ... 26+Sons%22

I think I may have discovered another clue about the internals. The opening of the top of the body has a spot welded inner collar added to the shaped upper shoulder of the body. This is below the cap roof. It is of two pieces of which the butt ends are brought together in a ramped valley. There are two of these notches 180 deg. apart. They are located 45 deg. off the axis of the two lens faces.
I believe these to be the detents for indexing the cylinder for the colored lenses.
I'm pretty sure this marker light was only white or green or off for selections.
No idea if this was accomplished with a flat or curved lens. There is quite a bit of room to "orbit" the light bulb.
The first pic is looking at the inside of the top from the center hole of the bottom. This bottom hole is girded by three screws. I think the attached plate mounted the socket, and possibly a guide ring for the base of the rotating inner cylinder. The fork at the end of the case knob could slip into the electrical switch shaft of the socket. I believe the bulb would be changed by dropping everything thru this hole.
You can also see the remains of something on the inside wall of the body above the indexing notch. No ideas on that detail yet.

Edit: removed because it is the wrong model and the size is annoying.

This is a tough one.

PMC,
The two patents listed on this thread (both the same) are of an earlier style lamp and are not the same as what I'm working with. Unfortunately the tag on my lantern says "Patent Applied" but no number given. I haven't been able to find it with the patent office site without that number.
I really don't think that the color lens mechanism is alike hence the "TurnTop" label.

Bob D.

Found a reference to this set of company archives in several places, but it looks like you need to travel to Cambridge MA to view it. If you go down to 33 it apparently has information on your class lights, and photos etc.:

https://www.cambridgema.gov/~/media/Fil ... .pdf?la=en

There is apparently a book about Peter Gray railroad products as well called Illustrated Guide to Peter Gray Railroad Hardware by Joseph F. Farrell, Jr., c. 1994 https://www.amazon.com/Illustrated-Guid ... rell%2C+Jr.

BTW Peter Gray Corp. apparently still exists and I found an address and phone number.

I live in Boston and visited Cambridge's archives. The only photo I found was the retouched one on the first page of this thread. No other info was relevant to 470's lights

The book about Peter Gray Lamps by Joe Farrell has long been out of print, but now and then a copy shows up on eBay or ABE.com (advanced book exchange) Joe passed away a few years ago and was a great guy, very knowledgeable about Boston area railroad history. His book contained many images and drawings of Peter Gray products, and was basic in its assembly, held together with plastic loop binding, probably 8 1/2 x 11 size. I sold my copy years ago on eBay.

Amazon has it for their Kindle for $7.00, it might be worth it to check it out if you have one of those machines.

I am really curious about the stash of Peter Gray documents in Cambridge, just going by that list I posted it sure looks like there would be detailed material on Peter Gray classifications lamps, including photos and possibly diagrams.

Thought people would be interested in seeing how the first replicated marker component is shaping up. Working on developing the lantern tops. Looks pretty close to what appears in the various photos we have found. The doming was done on a Bridgeport and rotary table using a technique called single point incremental metal forming. The metal is stretched similar to spinning but no form is used.
Bob D

Thanks to Wesley Heinz and our friends at Maine Narrow Gauge, we now know what the internals looked like!

These new photos have cleared up a lot of the mysteries of the construction of these marker lamps.
Bob D.

That's an incredible find, I wonder if the colored lenses were smooth or veined in some manner.

I wouldn't think it would make much difference, since the light still goes through the fresnel lens.

PMC,
The colored lenses were flat plate colored glass, 2.5"x 2.312" Only two of the four light ports were set up for these. Haven't found red or green glass to cut to size yet. I think a stage spotlight colored gel will work ok in a small metal frame.

Bob D.

Thought some of you would like to see some of the progress on the replication of these marker lights. Has been an interesting project that I bet has not been done very many times.
Bob D.