Atlas starter lamp for fluorescent circuits

I spotted this in an old wrapper in a box of lamps on Facebook marketplace and was instantly intrigued. After asking the seller what was inside I couldn't quite believe it when I saw the starter lamp! Luckily he was willing to send it to me separately. These lamps were designed as a ballast for certain types of streamline Atlas fluorescent fittings made in the 1950s and 1960s. This is quite similar in principle to the ballast lamps made by Philips, one of which I also managed to find in a lot about a year ago now.