Depends on condition and whats included. Just the gun I'd say around $450-500 around here. Add the box, paperwork, cleaning kit and screw driver the price goes up.
From a collectors standpoint the 15 no dash was made only in 1957. So it would be one of the scarcer model 15's. Also it should be what is known as a four screw example. (Three side plate screws and a trigger guard screw). The are desirable and sought after by collectors. If you can get it at a decent price I'd be all over it.
ETA: S&W says that any of their all steel, model numbered guns can handle +p ammo. But they caution that doing so may accelerate wear. We used 15-2's and 3's with nothing but +p in the Air Force. They held quite well.
Also the correct grips for the gun should be a set of diamond magna's like the ones on this model 14.