New to the Parker questions

[Drew Hause]

Welcome Wesley. Bright shiny bores in an almost 110 year old well used gun suggests that the previous owner cherished and took care of his treasure, or that possibly the bores have been honed. ANY vintage double deserves a good check and clean by a double gun smith before use, with measurements of the barrel wall thickness and examination of the stock head for cracks.
You may then have confidence that you can enjoy the gun with loads for which it was designed; the original Parker hang tag probably listed 1 1/8 oz. with 3 Dr. Eq. or 1 1/4 oz. with 3 1/4 Dr. Eq. (both about 1200 fps). And the pressures of those loads with Dense Smokeless powders were quite similar to today's. The barrels of course were not designed for steel shot.
No. 2 frame 12g Parkers are quite sturdy. I had a 1 1/2 frame VH which was a wonderful Kansas/S. Dakota pheasant gun using B&P MB Classic 1 1/8 oz. 3 1/2 Dram Eq. @ 1330 fps 5s.
It might have 2 5/8" chambers designed for 2 3/4" roll crimp shells; of no concern with modern 2 3/4" shells.