Jonas,
I have a very old manual for the Graduate that shows the beartings to be
Headstock Front - LJ40 - R&M Imperial Deep Groove - 40x80x18mm
Headstock Rear - XXLJ50 - R&M Imperial Deep Groove - 50x80x16mm
Whether you Graduate is old enough to have these bearings, or if the 2 identifed above are the modern numbers for these bearings I don't know, so I've posted this information - just in case.