I’m not sure about the extra thumb wheels. I had two others one 59 burst and a 57 gold top with humbuckers the back of the tuning head was black on the 57 both of these were players they all would sustain indefinitely but the neck pickup in curly was the best any of us had ever heard. Bob was a dealer out of Phoenix he would know the answer unfortunately he passed several years ago. He had his hands on most of them but when we would get Curly out at my Christmas parties and played in the back room he couldn’t stop smiling or put her down. He always said this is the Mona Lisa of the Guitar World! That being said maybe the extra nuts had something to do with it. Whoever built her must of been proud of there work and all of the owners of her knew it would be shame not persevere this work of art. I was truly blessed to watch over her during my turn.As I recall some folks think it gives greater sustain......tried it once myself with an inconclusive result.