Got this bulb around 1991/92, when a local book store went out of business,
According to the store owner it was the lamp sold as spare for one of the city lighthouses. Peniche has a main light house, two at the harbor entrance and a small pilot light on the north side. The lamp is "only" 300 Watt's, so I suspect being true the story, it would be for the small pilot light marke "L Fl R 7s" on the map. Translated from "nautical": Long Flash Red with 7s off period:
The last time I power it on was when mains was still 220 V, now with 234 V and the age of the lamp don't know if will risk it again (maybe in series with another lamp). I couldn't find the matching ceramic bulb holder, I know I have it somewhere....
Look at he size against the Hameg scope.:
And the Sailor receiver:
Still didn't found a good use for it but I really like the unusual size!
Have a nice week!