[vidjoman]

RS was the 'one stop' supplier of components to the radio/TV trade back when they started and R&TV manufacturers restricted parts to their own dealers. RS could supply most general parts and many special parts by return of post. They had reps on the road who would call into the shops in their area on a regular basis. They had samples in their little grey box to show you and the prices were competitive.
They had a catalogue stapled together from sheets printed on a Gestetner printer.
They had a reputation for quality parts, at least as good as the major makers, who often made the parts for them anyway. They grew by expanding into a wider range of electrical/electronic parts to be one of the largest distributors of these products.