In 1969 Gibson introduced their first Low Impedance Guitars — the Les Paul Personal and Les Paul Professional Guitars. The LP Professional has a Les Paul style body but slightly larger than the regular LP. The key feature of this guitar is its two low impedance pickups. These pickups give a very clear signal but require a special lead with built in impedance matching transformer. According to Dave Gould only around 118 LP Professionals were made - this is a relatively rare model. A Bigsby vibratio was an optional extra.
The Les Paul Personal and Les Paul Professional were replaced by the Les Paul Recording model in 1973. The 1970 Gibson catalog describes the Les Paul Professional model as follows:
The Les Paul Professional has many of the same exciting features found an the LP Personal: low impedance pickups: fast, low-action neck; and a 24.75" scale. But perhaps the feature you'll enjoy most is the model's price tag that accompanies this "professional" guitar.
FEATURES: Low impedance electronics and pickups. Clear grain British Honduras mahogany neck construction. Buffed and polished clear walnut finish reveals the fine grain-lined features in the basic wood. Bound rosewood ﬁngerboard with deluxe pearloid inlays. Nickel-plated Schaller machine heads with sealed gears. Nickel-plated Tune-o-matic bridge. Dimensions: 18.25" long, 14" wide, 2" deep: 24.75" scale, 22 frets, neck joins body at 16th fret.
Link: Dave Gould's info on Gibson low impedance models