Hey Jerry, here's some thoughts. If the seat stay bridges were drilled at the factory, I would think that they would have braised a tube in the hole to keep the bridge tube from being crushed. (And yeah, I have seen crushed bridges.) If there's tube in there and especially if there're traces of the original paint in the tube, it was probably done at the factory. You can identify some "amateur" drill jobs visually because they're usually done with a hand drill and the alignment can be slightly off. Front to back as well as side to side. The factory used a drill press and a jig so the holes will be centered and in perfect alignment. And by the way, some heretics are not above buying track frames and forks that somebody else drilled, but that makes them "enablers." Kind of like buying stolen property. Okay that's a little harsh, but I get grumpy when it rains and I miss my daily ride.