MWAK, an acronym for Mason, Walsh, Atkinson, & Kier, the contractors that won the bid to build the first half of Grand Coulee Dam, also operated the railroad. This would explain lanterns embossed with the letters "MWAK" being in existence.
I know of 3 of them. One, with a blue glass, is in the collection of the Inland Northwest Railroad Museum in Reardan. Sean Rotinski owns one with a red glass. I own one with a clear glass.
Sean and I had ours lit up for an event in August 2024. We'd like to get to a point of having all 3 lanterns together for a photo shoot.