Butterfly chair came fluttering into my life (Status: Knoll?)

I was on my way home from the vet when I spied an estate sale sign; I told the kitten I had recently rescued, that he was going to have to chill for a few while I took a quick poke around.  Man, did I miss a good sale!  If I had been waiting at 9:00A.M. I would have had a shot at a house full of vintage Knoll and Herman Miller furniture (Apparently there had been a Florence Knoll sofa, A Saarinen womb chair w/ ottoman plus a tulip table w/ four chairs, some sort of Herman miller desk and bedroom furniture)- sigh.  What I did walk off with was this solid frame, leather covered Hardoy "butterfly" chair.  Based on the rest of the furniture, I feel confident that this is by Knoll.

I have searched the interwebz high and low for a way to definitively confirm that my chair is a Knoll Hardoy chair (that's the proper name folks- "Hardoy" not butterfly) but it seems that the world is overrun by cheap (and not so cheap) knock offs that it is possible only to narrow down whether it is possibly a Knoll.  Knoll only produced the chair for two years and quit because there was no way to stop the tidal wave of knock offs; indeed this style of chair is the most produced style of chair in the world!

 To possibly be a Knoll it has to have a solid frame, Knoll NEVER produced a folding frame Hardoy chair.  and the frame has to be of iron, not steel or aluminum.  Beyond that...  who knows, there may be some measurements but I couldn't find anything definitive.

 So, mine has a non folding frame....

 and it is black painted iron....

 It was in a house full of early Knoll and Herman Miller.  I'm pretty sure it's a Knoll Hardoy chair.

 This is the original leather, which is nicely distressed.

 My chair has these thick rubber floor protectors (are those a Knoll trait?  I don't know)

 I probably over paid because I was paying too much attention to the frame I missed some issues with the leather (D'oh!).  The stitching at the bottom of the seat has started to come apart

At the top of the back, the leather has torn at the stitching.  These are common problems as the leather ages and dries out; a new leather seat can be procured from a Canadian company on eBay for around $150.  Make certain when ordering a new seat that you order for either a folding version, which tends to be a bit wider or a non folding version, which is more narrow.