Antique? Vintage? Light Bulb Very Unusual - weighs 6 oz - feels like solid glass

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Antique? Vintage? Light Bulb Very Unusual - weighs 6 oz - feels like solid glass:
$5.99

This is a very unusual light bulb. It was found in the attic of an old house. I have taken it to several lighting stores and electrical shops. No one had seen one like it before. The prevailing thought is it is a bulb designed to be used in a hazard area. It is about 4\" overall length. Look like a normal bulb it is very heavy weighing 6 oz. It feels like it is solid glass. You can see the elements inside but barely. The only marking is the number 3 near the base of the glass on the bulb. It does not appear to work in a normal light bulb socket. A great fellow er provided the following information! Thank You!
Your bulb is newer-type \"Capsylite\" made by Sylvania-OSRAM.
Molded Glass is thick to contain inner Halogen bulb in case of breakage.
There was also a diode in the base to operate the bulb on rectified DC.These existed in different wattages,styles. The most ornate was a 75W
Post-Lite,with decorative faceted pressed-glass envelopes.
Capsylite was discontinued in 1996 due to mechanical issues and
competition with CFL\'s. LED lamps have now superseded all of these.