If it has twist barrels and some sparse engraving, it likely is a P grade. G grade guns would have damascus barrels from my understanding. I have 2 G grades (grade 2). I believe the P grade is grade 1 and should be so marked on the frame watertable. The barrel lower lug surface should have a number marked in it. It could range from some multi "0" number to something like 3 or 4 or 5 at the heaviest/largest frames. If a 12g, most common seems to be a 2 frame size and #1 frames like my two are less common and I personally prefer them for their generally light overall weight.
