My understanding was that they were 320 mm long. (12.598")
I'll have correct, made from original drawings, rods available as soon as I have time to slot them.
From the examples I was able to get measurements from, originals vary quite a bit, even from the same manufacturer. They were not a "precision" item. Lengths, diameters, small features, all varied.
Interesting to know about the D.F. marked guns, I did not know that. I have one, but did not notice that it was any different. What is different requiring the longer rod?