If you search for electrolux~137’s Kirby 500 series history you will see that the 509 was the last model that had the smooth wand and the 510 was the first model that had the ribbed wand.
The mid-year production of the 513 was the first Kirby with a red grip (it was gray when production first started). When the 514 superseded the 513, the red grip was changed to the more common style that ran through the 561.
Hi, The mid section of the handle was smooth/plain up to the Kirby 517.
As it say on Mr Lesters site under the Kirby 500 series section 517/518/519...
"Middle (longest) section of handle became ribbed, not plain, metal tube. First rib design had the ribbing spaced about 1/8" apart and rather fine -- not very deep. Later, the ribbing becomes deeper and spaced much, much closer together -- (and that same style was used until the hideous-green Sanitronic D-80 came out, when a new plastic handle was introduced)."