If missing original stocks or the stocks are torn up, finish is average or worn, $350 tops.
If the pistol has a decent finish and one magazine, no box, $350 to $450 is typical.
If the pistol is gorgeous with hardly any flaws and has original stocks in fine condition but no box, $500-$550 is the area.
If it's nearly mint or better and with the original stocks, with both magazines and the paperwork in the box, it probably trades from $600 to $800 depending on just how flawless the finish is.
The 39-2 is attractive, fits the hand nicely, quite historically significant, is much loved, is fantastic to own and shoot and collectible -BUT- the market is not catastrophically high because S&W shipped over 347,000 of these pistols. For all the good, they are not rare and they are not scarce.
I've got three 39's and I'm sure I'll end up with a couple more.