The numbers system came into play long after I learned chords, which was 1945. I picked up my first guitar in 1952, though.
The Nashville Number System is a method of transcribing music by denoting the scale degree on which a chord is built. It was developed by Neal Matthews in the late 1950s as a simplified system for The Jordanaires to use in the studio and further developed by Charlie McCoy.
Gary
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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)