You mean the AF 105 mm f/2 Nikkor DC? This is a specialised lens with a unique 'DC' (= defocusing control) that allows the user to change spherical aberration and thereby change the appearance of the zone of sharpness in front of and behind the plane of focus. This feature can be very useful, but difficult to master. Be warned that its AF is by 'screw driver' so is quite slow and noisy compared to the AFS kind. AF is also inconsistent due to the DC as there is, at certain DC settings, no true optimum focus in planes perpendicular to each other on the optical axis. Manual focusing is pretty smooth and many myself included prefer that over AF. It has a rear-focusing variation of the internal focusing (IF) principle so length is constant during focusing. There is the vulnerable A/M ring that is prone to breaking. Don't use that control; set the lens to 'M' and tape the rotating ring into position of seal it with a few judiciously placed drops of epoxy. Repair to a broken A/M ring is very expensive and you actually risk that the lens breaks into two (this happened with my sample).
The lens hood is built-in and for once can be locked in extended position, but beware the threads are very fine and can easily jam, cross-thread, or bind, even permanently, if you aren't careful.
Handling is nice, colour rendition is beautiful and so is bokeh given you master the DC settings. Sharpness is very good to excellent, but the lens needs to be stopped down a little lest residual aberrations should give a soft-looking overlay to a sharp core.
Thus, an uncommon and potentially difficult to use lens that can be very rewarding used for its intended purpose, viz. portraits or details.
Ensure the copy works well and the aperture isn't sticky. Manual focusing should be smooth with a little but evenly distributed drag to it. Look out for evident cracks around the screw(s) of the A/M collar.
A reasonable price for a clean sample would be 2-3(4) times that of the 105/2.5 and 1.5-2 times that of the 105/1.8 Nikkors.
