This bulb is specially designed for rough service applications, specifically those in which vibration is a major problem. The filament is held in place by an astonishing number of supports: 18
! It's rated at an unusual voltage: 250v. It was probably still meant for 220v, a voltage at which a 250v bulb would burn cooler and thus last much longer (in the same way very long-life bulbs for 120v circuits are usually 130, 135, or 140v, such as in old incandescent traffic signals). Definitely a tough bulb! I don't know when it was made, but my guess is it's from the 60's or 70's. Any additional info will be appreciated.