If I have a very rare coin are they knowledgeable enough to validate it? And are they trustworthy to be completely fair and honest?

Very Honest, if you want to know exactly what it's worth coin & vault is the only place to go, I'm from out of town state and when I'm in Spokane coin & vault is the 1st place I stop. Most HONEST & TRUST WORTHY COIN DEALER IN THE NW PERIOD

They have been in the business for decades. Very knowledgeable and very trustworthy.

I find these people are very good, they have given me highest dollar on coins I have brought in, and also verified whether rare or not