thats a very awesome find,
the fine details of the lamp can be had from James's writeup on one on his website
http://www.lamptech.co.uk/Spec%20Sheets/D%20MBR%20Philips%20HLRG400.htm
Yep, that's the one! By now i did find the etch with the help of the site, it's just a bit hard to find on the pearl surface. Pictures will follow once the whole setup is complete.
It says base up as well as universal at the burning position. Is the 'universal' correct?
With the arc voltage drop of 145V and the operating current of 3.2A, it is more or less interchangeable with virtually all other 400W mercury vapor lamps in the world.
The ballast will follow the lamp as soon as the previous owner has found it back. It's not an 'orphan' lamp