I speculated in the Vintage forum that this is a mid-'20's conversion of a 'teens A-4, from eight to twelve strings, which might account for a retrofitted truss rod and the '20's logo on the extended headstock. #Where Gibson dug up the four extra Handels is another question; you can see that the four tuners closest to the nut, are "half strips" of the pre-WWI tuners. #Perhaps cannibalized from an unrepairable instrument, or maybe there were a few sets still lurking at the G factory. #In any case, a true rara avis.
Gibsn: '54 F5 3pt F2 A-N Custm K1 m'cello
Natl Triolian Dobro mando
Victoria b-back Merrill alumnm b-back
Stradolin Vega banjolin
Sobell'dola Washburn b-back'dola
Eastmn: 615'dola 805 m'cello
Flatiron 3K OM