IIRC they are a masthead Doug Petersen quarter tonner. Probably a bit heavy compared to the opposition, and the masthead rig doesn't work too well on small boats like this.
The Contessa 25 design that I know was a quite pretty little Robert Tucker designed cold-moulded wooden hull with a shallowish draught lead fin keel - generally looked a bit like a bigger Corribbee. There could well be another design with the same name, but I don't think so. I contemplated buying one once. No relation at all to the Contessa 26/32 etc from Jeremy Rogers/David Sadler.