Hi,
Hope you will get the answer from one of the other experts to confirm what Little Persia told you... From my 1-year old internet knowledge, I have never seen a rug that looks so much like an Isfahan and is not...
As far as I know (from the internet of course!) these coloured warps are more often than not absent in Isfahans. I had a small rug posted not long ago, no signature and no colours on the kelims, still was deemed an Isfahan. Internet says that the kheft measure is a bit like the raj measure, you take 6.5 cm and see how many knots there are? But agree that it would be interesting to know who started the colouring in Isfahan rugs for making that counting easier and who of the weavers follows that. No matter what, beautiful rug you have and really good price!