That’s the bearing completed and filled with 2/3rds “Singer” sowing machine oil and 1/3rd single grade SAE 20 motor oil. The old fashioned stuff (without detergent, anti foaming and dispersal additives) they use on classic cars/bikes. I did a lot of experimenting with oils on the Thorens bearing, proprietary brands and DIY mixes. If the oil is too thin it will spin really well, that is, fast and long but the sonics are not good, harsh and bright. Likewise, too thick and the sound can be dull and smeared. Until I did some tests of my own, if you’d told me the oil in the main bearing can make an audible difference I wouldn’t have believed it. When fitting the spindle don’t over fill it with oil. Apply only light pressure and let it slide in slowly, this may take several minutes. Too much force and the hydraulic pressure may defeat the gasket at the base and cause a leak so take your time. You can always fill the well at the top and let it work its way down over time if it is under filled.