F units were built with four sander fillers you see in the Photos here, the MILW just removed the filler cover doors and put on a different style lid. The EMD filler doors would sometimes get cranky and hard to deal with and some roads removed them as shown here. The filler holes stand out more with the EMD lids removed. Some roads in later years removed the inner fillers on their units--BN did this to some units (and not just to F-units). The Reading T-1 you mentioned had firing issues due to a poor firebox conversion and never generated steam at full capacity, as a result it wouldn't pull squat!!