Yep, just a drum brake. They're rather uncommon, but I've been seeing them lately on Trek Sohos. Apparently they're good for a commuter because they're unaffected by weather (much like a disc brake.) I'm not sure why the bike in the CL ad has one. It seems way out of place.

Actually, now I'm curious. Since disc brakes are on bikes now, why do they still make drums? What do drums have over discs?