Looking closely, it's either been back to the factory for upgrades, or someone else worked on it. The adjustable nut wasn't around back in '74. Also there appears to be some type of string guide posts added to the headstock. This is a pretty cool mod, IMHO that deals with one common characterisic of some early Alembics - the tuning machines were spaced in a manner that resulted in the strings touching each other after they went over the nut, on the way to the tuners. (My '76 Series 1 guitar has this). The brass thumbrest on the corner of the bridge pickup is tres cool!
Bill, tgo