Another thing I finally got rid of. I had box of old Märklin train stuff I sold a year ago or two. I kept this one, as the cable was pretty bad, and this device is not something to meddle with, imho. Hence the cut cord. Looks great and is heavy. It is from the 1960s, well before digital made it into the model train world. About as vintage as I am.
We used to call a transformer like this a "trafo". It seems in English they might be called "throttle control". Weird.
The text on back reads "AC only" in Norwegian, Danish and Swedish. The rest is German.
The "S" mark on top is apparently still a "standard" in use, though not sure I have seen it on anything for years. It used to be on every electric thingie of good quality in the old days, before the CE mark came around.