I want to know what the set of leather belts with bells are for.The
belts are numbered 1 to 15 and each belt has ten bells with same size
bells on each belt,though all belts have different size bells on
them.They are quite old

I wonder if this may provide a clue:

Every year, the ?Carnaval? festivities bring their own brand of
excitement to a number of towns in Wallonia. Each celebration has its
own folklore, costumes and music. Carnaval, which falls just before
Lent, is a time of great colour and excitement.

The Gilles of Binche dance to the rhythm of drums, chasing winter away
with the sound of their clogs and ?apertintailles? (belts with bells
on).

http://www.wallonie.be/en/decouvrir/decouvrir_wallonie/culture/folklore_traditions.shtml

Sounds as if you're missing one belt for the 8th reindeer . . .

It might help to see a picture. 

Kriswrite