Light seals, but that's common with all vintage cameras really. There's nothing really specific to those cameras (i.e. there's nothing unique to it, say like the Canon 'cough' for the A-series of cameras). Most of them are pretty bulletproof - don't forget, it's Harrow Technical's line of business to list as many faults as possible, and the chances are you'd only ever maybe stumble upon one of those, if it all. It's just everything that they have ever run into with these cameras.