To further clarify the info from Bulldogboy, I have gathered more info from one of Harvey Eckart's books on Mack fire apparatus. Mack built 381 R Model chassis specifically for the Fire Service, the last of which was in 1990. This number includes those completed by Mack Trucks and those completed by other manufacturers. Those completed by Mack will have a model number of R6??F- (the ?? indicates which Mack motor was used - 08, 11, 12, 85, 86, 88, or 90), followed by the 4-digit production number. Those completed by another builder would have a model number of R6??FC-, followed by the 4-digit number. If there is no "F" or "FC" in the model number, it is simply a Mack commercial chassis that was built into a fire apparatus by some other manufacturer. In addition, there were 23 Model R487F or R487FC fire chassis (Scania Diesel) built, beginning in 1972. When production of the R Model ended, over 210,000 had been built, with a mere 381 groomed for the Fire Service.