I don't know the background and will look into it, but cl(reverse
c) = 1000, l(reverse c) = 500. c of course = 100, etc. Note the
value for 1000 looks like the letter m, as in the Latin mille or a
thousand. l(reverse c) looks like the letter d, as in the latin
dimidium mille or a half thousand. I have never read anything
clarifying this, but this is my own supposition. Why the letters,
in roman dating during the early days or printing, should be
written in that way, I don't know.