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  1. I'm dropping this in the Chat About Anything Here topic as the subject pertains not to a timepiece but a rather a different instrument- a prismatic compass. I've been told an important part of any watchmaker's kit is a compass which can be used to determine if a mechanical watch is under the influence of magnetism. As the theory goes, place the compass next to the watch and if it's magnetized the compass will point to the watch instead of magnetic north. Perhaps this little bit of kit would have saved me some work in the past although I've been in the habit of demagnetizing watches before checking them out for sometime. Back to the story: my wife gifted me a nice liquid dampened lensatic compass several years back when we were still dating. She's well aware of my fascination with any instrument under glass and even tossed in a how-to booklet for orienting. Unfortunately between moves the compass disappeared. On the hunt for a replacement I began searching for a Francis Barker Mk III or M73 compass since they are considered the best in the business and I had long pined for one. Fortune favored me as I discovered a 1943 model, produced under license by the Canadian Kodak Company, in Greece (and in poor repair). The price was right so I made the purchase straight away and anxiously awaited my prize. This particular compass was produced Commonwealth soldiers during the war. The term Prismatic comes from the technology used to deliver a bearing to the user- a small prism built into the compass magnifies the reading on the compass rose which is visible as the user peers through the sight. The compass is also liquid dampened with kerosene; the liquid softens the movement of the card as it settles on a bearing. Luckily for me the poor condition of the compass assured it's delivery. You see, these compasses were painted heavily with luminous paint containing Radium 226. The Radium isotope is still highly radioactive today and there are many stories online of customers purchasing these antique compasses only to have them confiscated at the US border and destroyed when the Radium sets off alarms. The kerosene within my compass had long ago leaked out taking much of the Radium with it and rendering the compass relatively inert. My plan is to completely restore the compass to the original specifications while replacing the Radium paint with either Tritium capsules or Superluminova. Thus far I've only completed disassembly which you can see below. I'll update this thread as work progresses hopefully from start to finish. Here is the compass as received. The bowl containing the kerosene dampening fluid is empty now and water has entered at sometime resulting in oxidation and clouding of the crystal. Step one was to remove the rotating bezel which then gave me access to the eight screws sealing the bowl. The crusty white paint is either just that or Tritium or Promethium luminous paint as it gives of very little radiation. Originally it would have been Radium based luminous paint. Two small screws on the exterior of the compass secured the bowl to the housing. With the bowl opened and the card out you can see a bit of radiation is still present. The compass card would have been painted with Radium 226 inside the small lozenge pointing north. Also the card, which is cut from mother of pearl, is tranluscent; lying beneath the card inside the bowl is a small tray which also would have been painted with Radium 226. The copious amount of luminous paint would have guaranteed usability of the instrument during the dead of night. Various issues were uncovered during disassembly- the first being the oxidation of the magnetic needle. A lot of rusty debris was left in the bowl which came from the needle affixed to the bottom of the card. Water had entered the bowl at sometime oxidizing the only iron based component in the entire assembly. The needle must be magnetized in order for the compass to work properly so the rust may be a big problem. Furthermore, the water was clearly contaminated with Radium 226 as the needle is now highly radioactive. in the end I may need to replace the entire compass card. Here is a view of the debris accumulated inside the bowl. Which came from the mother of pearl compass card. You can see the printing of the compass rose is still quite crisp. In the center is a clear sapphire bearing (much like those found in mechanical watches). The underside of the compass card is a right mess though and since the rust is impregnated with Radium I'm not I can chance cleaning it. Secondary issues discovered included some not so nifty repairs from the past. The crystal within the lid for example was not a great fit and needed some help in the form of epoxy and an ill fitting gasket. Many screws had damaged heads too. This is the filler plug which has been manhandled in the past and sealed with a bit of epoxy. The gasket for the bowl was also a poor fit which is probably why the dampening fluid was missing. I've begun research to determine the proper material for a replacement- it will need to stand up to prolonged exposure to kerosene so natural rubber will not do. This job requires many of the same skills used in watch repair as the parts are small and made of soft metal (brass). With disassembly complete I'll move onto cleaning and have already begun researching replacement parts. When the job is done I'm aiming for a vintage compass which looks about as good as new and functions the same way. It's a lot of work just to check the magnetism of a watch movement but in my opinion restoring the tools is as much fun as restoring the watches.
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