I'd scarf that up in a minute! Check for the model: if its the "Three Screw" model or New Model. The Three Screw model is pre-1973 and lacks the transfer bar safety (maybe) and can be identified by the three screws with slotted heads in the frame. If its the New Model it will have two pins in the frame, no slots. Also the hammer will have a notch in its face when the hammer is pulled back.
If it is a three screw, it may have been converted by Ruger to install the transfer bar safety. No matter which model, $300 is a pretty good price.
Unaltered Three Screw Models usually bring slightly higher prices as they are more desired by Ruger enthusiasts, especially if unaltered.
P.S. Blue, or stainless? Grips, wood or black plastic?