In response to your question, this is probably a "value branded" sign lamp imported from Japan. We used to get thousands of cheap brand light bulbs from Japan, Austria, and Germany. I too have a similar sign lamp with three loop carbon filament (that's what your bulb has too), made in Japan. Speaking of your base not fitting in an Edison socket well...it might be because of the corrosion on your base, or the base might have not been fabricated very well. Japanese light bulbs at that time (before WWII) were made with very primiative technology. I have also experienced diffculty inserting a few Japanese lamps...but those I had problems with have candelbra bases (small size). Hope this helps!