@Brit64,
we are leaving for PEI by sea today. We will be back home to pa probably by the 14th or there about.
What sort of a document do you own? Does it have some historical interest? Is it dated or signed.? HAve you determined that it is old?
Any idea why its nailed to a board? IS the board old?
How did you determine age on the paper or board?
Youve got homework to do and Im afraid that I cant help you because sombody who better knows what theyre doing (not a poster on the internet like me) NEEDS to inspect whatever it is you may have.
Having said that,
Finding someone who is capable and totally honest is often difficult. Many people want to buy whatever it is you have , for a bottom price so they can sell it at a hefty profit .(That is , if what you have is even worth it)
Id find an ephemera curator at a museum like the WInterthur Museum (which is a world famous art conservation and research lab and museum run by the University of Delaware through several Dupont Family Foundations.)
There are other museums with research fcilities all over the world, of course, but Winterthur is the one with which Im most comfortable.
They have many experts in many disciplines of ephemera (paper, cloth, wood, etc etc) on their staffs and they can help you with the authentication, valuation nd even marketing. (They, will, of course, probably charge a fee for service but Itll be honest, and in -depth).
Winterhur runs classes on connoisseurship and conservation and they specialize in exposing "fakes and counterfeit " art and all kinds of antiques.
Good Luck. ill be here till about 11 AM today when we cast off and will be sort of out of touch for a few days till we dock and trade papers with the Canadian Govt. and the boats owner( or in whatever order they specify)