Is it a 5 shot or a 6 shot?
If there is a model designation stamped under the yoke, it was made after about 1957. If none, it was made before then.
If it has a model number, it probably will be a Model 12 if a 6 shot or a Model 37 if a five shot.
You can also narrow down the date of manufacture by the existence (or absence) of a screw on right side of the frame near the top (by the hammer); and by the existence a screw along the front, center, outside of the triggerguard where it joins the frame.
The first screw was dispensed with maybe 1955 or so. The second screw was eliminated maybe 1961. I believe these dates can vary a bit depending on the model.
Actually, it should be pretty easy to track down the date of manufacture based on the serial number.
Price sounds a bit high, esp. if it’s a model 12.