I expect the Yugoslavians did use the metric system in their nomenclatures. However, in discussion with the Zastava Historian, he converted the dimensions to closest inch measure I guess. Anyhow, those are the figures he gave me just as he sent them.
I've seen several variations in "inches" for the M48-M24/47-M24/56C. 4.5 to 4.75 inches is the common answer.
Keep in mind, the M48- 24/47 are entirely different manufacture and origins from the 24/52C The "correct" cleaning rod for the 24/52C would most likely be whatever was issued with the vz24. The 10" & 12.5" rods were specified for "K98variations" which would include the 24/52C with its standard length action. I don't know what was standard to the vz24 and I don't know if the Yugos bothered manufacturing shorter rods for those actions or had enough on hand. Interesting question. I'll ask about it.