I found the service manual on
http://www.elektrotanya.com. This is an excellent site for finding service manuals and technical information.
Page 63 shows one belt, reference 159, part number 4-219-326-01, description "BELT (DIA. 42X1.2)".
Page 64 shows two belts, reference 206, part number 4-216-061-01, description "BELT".
So it looks like there are three belts in the unit, and two of them are the same but the third one is different.