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Author Topic: Can you identify this bulb?  (Read 15632 times)

Offline timmc

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Can you identify this bulb?
« on: January 20, 2019, 06:23:08 pm »
About 10 years ago we found a box of old bulbs in a storage unit.  We don't have any information on them, but we did sell a couple on ebay.  Someone mentioned that they may be switchboard lights, but I haven't seen any switchboard bulbs that look like these.

They have a number printed on the glass (I pulled out a few and saw 300 and 500 printed on them).   At the base on the metal, there is a handwritten number (different numbers).  Can anyone 'enlighten' me as to what these are and if they may have any current value?  We'd be truly grateful.

Offline James

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Re: Can you identify this bulb?
« Reply #1 on: July 28, 2019, 02:37:03 pm »
These look like carbon filament barretters - also known as resistance lamps.  They were not intended for illumination, but as a particularly stable kind of electrical ballast resistor.  The number printed on the glass often refers to the electrical resistance value in ohms.