At one time I had a trailer with serial number 19, and, as Brian mentioned, the CFR did not match the serial on the drawbar, which was 70019. Stripping the paint did reveal that number on the body however. I suspect that the first batches of trailers out of MCI were more likely to match or come close to matchng CFR/serial, but as production sped up, the assignment would have varied more.
In the early 80s, as part of a re-life project for the trailers (and perhaps a little make work project for civilian companies) the majority of the trailers went downtown for sandblast and paint. This resulted in the plates getting mixed up. I mostly used the stamped CFR to try and properly match the plates to the trailers, but found several trailers whose stamped CFRs did not exist in our area. So some of the mix-up appears to have happened years earlier.
Scotty posted all the available serials in an old thread years back indicating somewhere around 1400+ trailers. Note that there are a few M105 1.5 ton trailers mixed in the CFR range.
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