Buttplate Replacement & Appraisal

[robert.adams]

I have a few questions regarding my grandfather's Parker Shotgun. Through information available on your website we have determined it to be a 1902 12 Gauge shotgun with a Damascus barrel with extractor. The frame size is 1 1/2 and it is parker grade 2. The gun is in relatively good condition with some scratches on top of the butt stock. The barrel is in excellent condition. The buttplate is non-original (Remington) but every other part has a matching serial number.

First of all, what does the 'G' mean on the water table?
Secondly, approximately how much would the gun be worth?

Also, if anyone knows the best place to buy a parker brothers buttplate for this model, please let me know.

Thanks,
Bob Adams