Steve, welcome to the forum. It looks like you have been bitten by the Parker bug. Be careful this is a lifelong desease.
From the pictures it looks like you have obtained a great shooting legacy from your family. You don't say where you live, but if I were you I would have the gun to a good smith and have it checked out. I can't count how many of us have a Parker like yours in our fowling arsenal. They are great hunting guns and a joy to shoot.
You need to join the PGCA as a member not just a forum member. The &40.00 that it costs to join up is the best money you will ever spend. You then are able to order a letter on your gun, this would be a great addition to the info you are gathering for your dad. As a forum member the letters are $100.00 ea. as a PGCA member they are $40.00 by joining and ordering the letter you have saved $20.00. That is a couple boxes of shells. The knowledge these people have is amazing. Some of the stories that are told here are unbelieveable.
as a member you also have access to the members only portion of the site. Whe you can buy and sell Parkers, accessories and other things.
Anyway, again welcome to the group, and enjoy the ride, you have embarked on a life long journey of friends, fun, and shooting.