Hi, And thank you for checking my post. I need some information on a lamp that I recently discovered. Background: I am the seasonal naturalist historian at Wilderness State Park in Michigan. The park is on Lake Michigan with a peninsula jutting out into the lake. Separated from the peninsula,depending on lake levels,are one or two islands. In order to reach the islands, you must take a boat. Parts of both islands are impenetrable. Very few people visit these wild areas and the ones that do stay along the shoreline.  On Thursday Sept.15th,2016, I kayaked out to the far island to continue working on a plant and wildlife survey. After walking around 3/4ths of the perimeter, I decided to cut across the island. This was a mistake as the forest vegetation is very dense. Every step was a challenge, with downed trees covering the ground and close growing cedars. So here I am crawling under and over dead trees in the center of the island. I look over to a patch of moss covered ground and see a light bulb just sitting on the moss. It is unbroken but missing the screw in bottom. It is clean and transparent, with no cracks. It says Westinghouse Mazda Vibration Service 50w 115v.
  Questions: This website has the same bulb posted by a member and shows the manufacture date as 1935. Is this correct? How long was this bulb manufactured? What was its primary use? Boats, planes?  I am trying to piece together how this bulb came to this spot and approximately when? It was not buried.
  During WWll, this island was used by the Navy as a bombing site and a target by primitive drones.  Any information related to this bulb would be greatly appreciated. If you have questions, I will be glad to share what I know.

Westinghouse and GE both stopped using the Mazda name in the 1940s, so the lamp is definitely not later than that. The envelope and filament shape look pretty modern, and there's no little "point" at the top, so I'd estimate it's not older than maybe the late 20s to early 30s. Some more knowledgeable people on here might be able to give you a more precise date range.

Also, my guess is that it came from a boat or from somewhere on land. I don't think many (if any) planes used 110-120v for lighting.

Welcome from a fellow Michigander! I live in East Jordan; not too far away. Any chance you can post a picture of the lamp? We like pictures!

This could be what was known back in the 1920s as a mill lamp.