From the smooth grips and the style of cocking knob its likely a 1944 or 45 production gun. If you post a picture of the markings on the other side the date and maker can be determined. Does the magazine number match the pistol? I don't keep track of sale prices but gun show asking prices seem to start around $5-600 and go up. Checking completed sales on one of the big on-line auction sites will give you an idea of real-world prices.