Sam, the same guy was at the range today with the 29 Classic. It's not blued stainless, it's blued steel. But it has a full underlug just like the 629. Here's a link to one on gunbroker.com that has a photo.
He also had another interesting Smith. It looks identical to the 586 (blued, .357, full underlug) but it's stamped 686. I couldn't see any difference between that gun and a regular 586.