Putting things in the correct order

I love to find little details around the canal network and in this case it is something I had missed until the sun was at the right angle, and then it was obvious. This is Bridge 14 on the Macclesfield Canal at Higher Poynton and if you look closely at the coping stones they are numbered from I to IIIIII. It seems that the parapet has been rebuilt at some point and that III and IIII have been transposed.