New to Forum Qustions About My Shotgun

[NowakPE]

Attached are some pictures for reference. I found this site as I was searching the internet for information on Parker Brother's shotguns. My grandmother gave me this one many years ago. Based on the serial number, it appears to have been manufactured in 1898. Where I get confused is in deciphering the other marks. This is a hammerless 12 ga with Damascus barrels. The barrels weight 3-10 and the frame size is 1 1/2, per the marks. The barrels also have a C and D stamped on them. Do these marks mean anything?

I am also confused in the grade. There is a 2 stamped above the serial number and a G stamped below. Dies this mean it is a 2GH shogun? Since it is hammerless, should it have a GH stamp instead of just a G?

I have not tried to polish or deep clean this gun as I was advised many years ago to not do that. Is this correct advice? The gun is not perfect as it has been used. Likely used a lot based on family history.