Since the neck on this D1A is different than the usual Collings (or Martin) neck you encounter on a recent acoustic, we'll start there: The Collings Vintage neck is for players who like the deeper, more "meaty" neck profile often found on vintage Martins from the 1930s. On many of those guitars, as on this one, the neck is only slightly larger in the lower positions--the first 3 or 4 frets--but then tapers up to a significantly deeper profile very quickly once you move past the 5th fret. These deeper profile acoustic necks are to flatpickers what the Gibson '59 Les Paul necks are to electric players, and they offer the advantage of giving the fingers of your left hand a helpful fulcrum. So while the initial reaction is that the neck is bulky, flatpickers often grow to love necks like this and find it leaves their hand less tired.
This D1A has only light fret wear, the surface condition is almost perfect except for a nick in the upper back corner of the headstock on the treble side (see upper left of photo 9). Neck mass does have a positive effect on both acoustic and electric guitars, this one has great balance and projection. Original case included.