Kirby Hose Designs 101
A HISTORY LESSON ON KIRBY HOSE DESIGNS
For models 505-515, the original hose had no suction coupler integrated to it. The suction coupler was metal and was available under part #2100.
For models 516 to Sanitronic 562, the suction coupler was thus revised but still made of metal. This version is part #210056. It could also be used as a blower coupling, which on 515 and older models was a separate coupling, part #2120.
When the Sanitronic VII, a near-identical twin to the 562, was introduced in 1963, the suction coupling (still not a regular part of the hose yet) was changed to plastic and it, again, could be used as a blower coupling. On the main hose, the coupling which the suction/blower coupler attaches to changed from metal to plastic.
When the Dual Sanitronic 50 came out in 1965, the suction/blower coupling was given a longer right attaching tab, so as to depress the safety switch speed selector arm down enough to accommodate the new high speed. The newer SBC is part #211063S for the Sanitronic VII and #211065S for the D50.
One year into sales of the D50, Kirby revised the complete hose assembly to include the suction/blower coupling already integrated on it, eliminating the prior attachment coupling used on the Sanitronic VII and older hoses. The 1966 version of the complete D50 hose is part #223666S. It continued on in this way up to 1981, in varying trim colors of course.
~Ben