Decades ago I spent a few years working in a small commercial darkroom. When the local Kodak sales rep would stop by he'd sometimes wander in to talk shop for a bit while I was working. As I recall, I could ask him just about any technical question regarding Kodak's products and he invariably knew the answer. Never had to "get back to me." And his answers were always correct.
Those were the days Kodak's sales reps were know as TSRs - technical sales representatives - and really WERE technical. I think that changed in the 1990s IIRC. They became simply 'order takers'.