I would say an original Maker's oak and leather case with accessories that is original to the gun would add 1K to the price.
I have a Boss imported in 1928 through A&F was sold to a guy in New York that has the address wrote in ink on the outside of the case.
It has the original one piece cleaning rod and original Boss oil pot. The case is in original un-touched condition.
This guy also bought two other Boss guns which a friend of mine owned the 12 gauge at one time. The other was a 20 gauge that was sold at auction in the UK in the past year.
