Hi All,
I got the required Information from Cox Mowers.
An extremely friendly lady (Lea-Ann) sends me an email as followed:

The 6899I Victa Corvette was made for Victa by us in 1999. Although very similar to our model 6999I it is not the same I have attached a parts listing for the machine unfortunately we do not have a copy of Victa�s Owners Manual.Regards Lea-ann.

With that information I went and ordered the belts:

BELA108 BELA108: VEE BELT A108 - COX / KINGCAT V26

BEL6860 V-BELT PREMIUM QUALITY A SECTION (68 SERIES) 60 INCH O.D. KEVLAR

Hope this info helps the next person finding parts for a ride on Victa Corvette 3212 Hydrostatistic, Model 68991
Peter (Hilfe)