Hi everyone

I' have been collecting for a number of years, however I am just getting into the extremely difficult area of double guns and I hope you can help or direct me to somewhere to get my answers.

1. is there a reference book out there for values on double guns?

2. I have a couple of books by Nigel Brown, (good material)but no value

3. I have been pondering a couple of old guns but am trying to determine value, first is a Anderson double percussion, finely engraved backlock hammer gun with Damascus barrels, it is complete and in fine condition, i would grade it at 75% plus condition. Second is a Joseph Lang and Sons, double boxlock 12 gauge 2and 1/2 inch chambers, ejectors, wood is in excellent condition , metal bits including barrel would need to be reblued and the action is a little loose. any help in valueating these guns would be appreciated.