I have a marked 936 (like the fully marked version of the 940). Does having a marked version increase the value over one that is not marked. I notice in the price book that there are some watches that are worth more with the actual grade marking.

You know Bruce, the fat book does say that most collectors prefer marked. I have two 936s and one is marked. The other has a four digit SN and I don't believe any Hamiltons were marked in that SN range. My 991 is marked and I've been led to believe that is special, but who knows? I would not trade it for an unmarked one.