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It is about 1 foot (30 cms) long. It is a hollow sealed brass object and has a bulb holder at the end, inside is a tube for a set of U2 batteries. It now looks like a pendant lamp with the globe missing. At the other end is a hook for the unit to be hung.

Your comments:

  • I agree with a couple of the other commentators that this is an illuminated dan buoy, used for marking a position at sea in the dark, especially when someone has fallen overboard from a vessel.

    Where the knurled nut is, there should also be a small glass dome with a torch bulb inside. There would be batteries in the tubular section, with a weight and spring arranged to form a gravity-operated switch. This would light the bulb when the unit was upright, with the lamp at the top, but switch it off when it was held upside down.

    The buoy would be stored in readiness by hanging it by the loop, in which position the light would be off. To deploy it, it would just be thrown into the water, whereupon it would float upright, and the light would switch on automatically.

    I suspect this one was made by a company called Easco. Santon was another manufacturer, but their models looked rather different. Similar devices, using plastics and LEDs, are still in use as essential parts of marine safety equipment.
    .......... Tom Edwards, Hertfordshire, UK, 4th of October 2016

  • External pressure actuator (bit like a barometer)? presumably internal pressure is created (via tyre valve)which pushes end with ring outwards away from centre of object - to a set distance. The double balloon brass shape helps this action by becoming distended. External pressure changes (for instance up in a balloon or down in the sea) would result in the overall length of the thing changing - hence the ring at the end which would I guess actuate some kind of action or gauge?

    Wild guess here but it would work as a deep sea depth gauge? causing some kind of action when reaching a certain depth?
    .......... tim, huddersfield, 9th of March 2014

  • It looks very much like a brass Plumb Bob
    .......... kevin Somers, Ireland, 18th of February 2013

  • I agree with the buoy description.It was battery operated and you had to hang it upside down to avoid the light to come on.Indeed the glas is missing and the light bulb connector as well. You had to screw off the glass and take out the connector to replace the batteries. I have used these for marking a spot on the water in the dark.
    .......... T.W.Wispelwey, Goenga the Netherlands, 25th of April 2012

  • This is a man-overboard light. It would be thrown in the water with a life preserver and would turn on automatically when it righted. It is missing the glass light casing where there is a screw bezel.

    There is no evidence of wiring or electrics on this unit. Curator.
    .......... Pete stone, Buchanan, MI, USA, 5th of October 2010

  • It looks a lot like a stop-cock for a toilet tank.
    The ring at the right end would fit over an "arm" when the chain was pulled to raise the stop-cock and release water from the tank, which used to be suspended near the W.C. ceiling, down through a pipe leading into the toilet. Thus was a toilet flushed.

    .......... p.m. clift, Montreal, QC, Canada, 4th of October 2009

  • Is it an apparatus to show the "power" of a vacuum?
    Magdeburg Spheres type! Evacuate and two persons pull the handles to try to part the spheres. But that would suppose that the two halves do come apart - perhaps the seal has solidified and permanently sealed the two parts?

    .......... Roy, New Forest England, 4th of April 2009

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