They crop up on ebay occasionally. Anything in particular your struggling with?
Does it have a dark blue hood? If so it'll be a 6525c, it should be cast into the metal chassis underneath, over the dirt chute into the bag. The ratings sticker should say it too.
Ive got a 652c,a rare crossover between the 652a and 6525c, the ratings plate calls it a 652a so presumably they did some casts before changing the model number completely.