No longer in production, but still fully supported by Manitowoc Group National Crane Distributors, the 18.0-ton USt (16.3 metric ton) lifting capacity National Series 600D Boom Truck features four distinct models within this product range.  Mounting options are Tractor Mount, Low Profile or Standard Behind Cab Mount, or Rear Mount. 

National 638D - 16' - 38' (4.9 - 11.6 m) boom with optional Model 6FJ15 15' jib or Model 6FJ25M 15' - 25' (4.6 - 7.6 m) two section jib

National 647D - 19' - 47' (5.8 - 14.3 m) boom with an optional Model 6FJ18 18' (5.5 m) jib or Model 6FJ29M 18' - 29' (5.5 - 8.8 m) two section jib

National 675D - 29' - 75' (8.8 - 22.8 m) boom with optional Model 6FJ25 25' (7.6 m) straight jib or a Model 6FJ45M 25' - 45' (7.6 - 13.7 m) two section jib

National 685D - 25' - 85' (7.6 - 25.9 m) boom with optional Model 6FJ25 25' (7.6 m) jib or Model 6FJ45M 25' - 45' (7.6 - 13.7 m) two section jib

The 649D and 657D model cranes were also produced in a limited production run within this Series 600D.

The National Crane Series 600D was followed by the Series 600E,  and as of 2022, National Crane is currently producing the 600E2 Series.