My question is:  Among the various manufacturer's of toy trains, when they describe the length of a car, do they measure the length of the car's frame, or do they measure from coupler to coupler; and whichever way they do it, do all the manufacturer's do it the same way?

It seems that in the case of height, they all measure from base of wheels to top of car.

 ???Is the car length given under Product Information taken from end to end of car, or from coupler to coupler.  Does not seem consistent between manufacturers?   For example, Williams O scale boxcar given at 10", and other manufacturer's car given as 11+ for O scale car.