I'd rather not venture a guess. There are other members who are better estimators than me. I will say that S&W made thousands of these models and they aren't particularly rare. Your Lemon Squeezer has what looks like a 5" barrel. That would bring a premium, but I can't say how much.
If someone doesn't get back to you soon, check out the completed auctions at gunbroker.com for guns that actually sold. That will give you an idea of current market value.