This bulb is what you would have normally used in the past for a "rough service application", or those in which vibration was a major problem. The filament is held in place by 18 supports, which is far more than you would find on a normal incandescent bulb. It's rated at an unusual voltage: 250v. It was likely meant to be used on a 220v circuit, and the 250v rating is for extended life, since an undervolted incandescent bulb would burn cooler and thus last much longer (in the same way very long-life incandescent bulbs for 120v circuits were usually 130, 135, or 140v, such as in old traffic signal bulbs). Definitely a tough bulb for its day, although these days any regular LED bulb can stand much more abuse than any "Rough Service" incandescent bulb ever could. I don't know when this one was made, but my guess is it's from the 60's or 70's. Any additional info will be appreciated.