F3A numbers SLSF 5005 and SLSF 5007 were rebuilt into a F9Am in the mid-50s. I am not sure what the "m" stands for. They were renumbered in 1968 as SLSF 75 and SLSF 77, respectively. F9B units SLSF 5140-5152 were all also apparently renumbered by simply dropping the first digit, as SLSF 140-152. I am not sure when the repainting from black and yellow "cigar band" schemes into Mandarin orange and white occurred. Frisco In Color shows what is called an F9B in mandarin orange and white in 1974, but the caption also notes that it is SLSF 138, which by the renumbering charts would make it an F7B.
The designation "m" normally means modified. For example if it had 1500 horsepower prime mover instead of 1750 horsepower. ATSF had a GP7m unit, ATSF 99, later ATSF 2899, which was basically a new built unit with serviceable components from a wrecked FT unit combined with a new frame, car body etc. The new parts were supplied by EMD to the Santa Fe and it was "kit bashed" together by ATSF shop forces in March 1954. This was right about when the changeover from GP7 to GP9 production was taking place. Supposedly GP7 production ended in May 1954 but GP9 production had began in January 1954. ATSF 99 ended up with the prime mover and 1350 horsepower rating plus certain other components from the wrecked FT on a new GP7 or GP9 type frame with the machinery housed inside a GP9 car body. Technically it should have or could have been classified as a GP9m as it looks like a GP9 externally. Eventually it was rebuilt by ATSF to become an actual 1750 hp GP9 and redesignated GP9 from GP7M. Frisco F3A SLSF 5005 and SLSF 5007 were not modifications by any means of an F9A. They were the old F3 units refurbished or rebuilt as brand new F9A units. As rebuilt they looked like a F9A but used the their original F3A builder's numbers. Being that they used the original frames and kept the original F3 serial numbers they should have be considered and designated as an F3Am. They have also been referred to by some as F9Am. As rebuilt they simply became F9A units and should be referred to as such and nothing else. Any units that survived long enough would have made it into Mandarin orange and white after the 1965 introduction of that color scheme. ALAF 138 was an F7B. The F9B reference in the caption was either a bonafide mistake or typographic error.
