I'd say there are about 5 to 10 working ones, in good shape, on Ebay a year. They are no different than any other brand; you're just paying for the name BUT the stainless steel model with stainless steel band is very nice looking, like the one below. Of course, like most manufactures of the 70's, they didn't make their own modules. They chose to go with the 25mm Hughes modules for their cases.
http://www.ledwatches.net/photo-pages/concord5.htm
Jeff