According to Terry Dean's Tractor Data Book.

Models prior to S/N 32001 are unofficially called Series I there were 29,988 built.

Series II Started at 1960 S/N 32001, 9540 were built.

Series III started at 1962 S/N 42001, there were 9126 built.

Series IV started at 1964 S/N 75001, there were 14213 built.

Series IV after 75001 and later have live hydraulics and a CAT 2 three point hitch option.

S/N 1001to 233633 have the tractor, grille and wheels painted Persian Orange with silver wheel rims and hood transfers.

S/N 24001 to 31625 are the same as the previous ones with difference of three black horizontal bars and border on a silver grille, and white and black hood transfers.

S/N 32001 to 41540 referred to as Series II with the tractor painted Persian Orange no.2. and the wheels and grill(no bars) painted a cream color.  The cylinder muffler and wheel rims are painted silver.  The hood has cream colored metal hood plaques.

Series III S/N 42001 to 72768 Have the same color as the Series II with changes being a large black oval muffler, and large cream colored hood  transfers.

S/N 75001 until the end of production are Series IV and are the same color as Series III, but have the series designation on the fuel tank decal.  The Series IV also have the hydraulics and hitch changes mentioned above.

MACK wrote: Series3 had heavier front axel, different brakes, few changes in hydraulic pump, hydraulic and PD oil together, dry air cleaner, belt drive power steering pump, and a few other miner changes.        MACK

Several of those were options.  I did not list the options, just the way you can tell the difference between the Series.  There are several other options, and from the looks of it they were available on all D17's.  The one that really surprised me was the Foot Accelerator, which was an option for the Industrial version.  I would think it could be put on any series if you had the parts.