Hi, this is a well-known lamp and bulb type, dating from 1929 or 1930. The bulb does in fact contain mercury. In operation it strikes an arc in the mercury vapor, causing a plasma discharge which puts out a lot of ultraviolet. The glass the bulb is made of was designed to filter out the shortest UV rays, supposedly making the light safe to look at without filtering goggles. I don't know whether subsequent research has shown the light is nevertheless harmful to the eyes or to the skin (as you probably know, sun tanning significantly raises the risk of skin cancer). There was an earlier version of this bulb made of clear glass, which was in production for only a year or so, and it is hard to find and very desirable for bulb collectors.
Several different fixtures were made that use this bulb (and another similar bulb called S-2, which is smaller and also was available for a short time in the scarcer clear glass). The fixtures all contain current-limiting ballast circuitry; these bulbs canot be connected directly to line power.
I have an original salesman's manual for the lamp and would be glad to share it; perhaps Tim, the administrator, would like to reproduce it on the site.
All the best,
Chris
