The correct stuff is a ISO46 viscosity turbine oil. The mobil DTE medium Tony linked to is suitable.
The issue is that additives in other oils can damage the sintered bronze bearing material.
I used to have one. Cost me the equivalent of about 50 euro around 1978, sold it for 10 times as much about 15 years later. It was a beautiful piece of engineering, very mid-20th century. Everything was big and strong and of marvelous quality. A pleasure to handle and to behold.Nothing to worry about, it is simple engineering of a very high standard. The main bearing in any TD-124 is somewhere between 50 and 70 years old. It is a design with a removable thrust-plate sealed with a gasket, and chances are this, like most of the deck, that will need some attention by now. Really nothing to fear here, it is a very well documented classic deck. There are many huge threads here and elsewhere on the internet documenting every last nut and bolt. It is one of the most significant hi-fi designs on the planet IMHO, well worth learning the service procedures.
Unfortunately I could never get a steady speed, it varied as the motor warmed up. I even had the motor re-wound, but to no avail. Was constantly opening it up to move the "drag" magnet around. At the time, pre-internet and pre- 124 Cult, it was all very difficult.