Warren Platner Garder Leaver chair.  

I was curious about this post...
I was curious about this post just because I am not familiar with the works of Gardner Leaver.
In googling as you said, it appears you are referring to this chair. Steelcase quite clearly states it was designed by Gardner Leaver. I think it is the first hit.
Or maybe you meant another chair?
http://timeline.steelcase.com/list/?phrase-1=term&modifier-1=LIKE&st-1=G...

Platner for steelcase
So, did Platner really design anything for Steelcase? I was researching these chairs awhile back and noted the different attributions. I remembered this old thread in which a designer for Steelcase stated Platner did not design the "soft seating" group either.
http://www.designaddict.com/design_addict/forums/index.cfm/fuseaction/th...

you have the correct chair. o...
you have the correct chair. on google if you hit steelcase Warren platner that chair pops up.. On 1st dibs they all say warren platner some sights say Gardner Leaver . Metro Retro on 1st dibs list 8 chairs for sell just like them by Gardner Leaver. I talked to steel case in Chicago. They have no idea, as that chair made in the early 70's has always been know as both Warren planter, and Gardner Leaver. It just depends what salesmen you get. Now I am really confused.

In matters of attribution, it...
In matters of attribution, it is usually the case, when there are two conflicting attributions, the correct one is the one of lesser reknown.
And I should think the manufacturer's website, as I linked, is deemed a extremely authoritative source.

The only companies Warren Platner designed furniture for was Knoll and Lehigh-Leopold. In 1969 he designed a showroom for Steelcase in Chicago, however did not design any of their furniture. The Gardner Leaver and Soft Seating collection are erroneously attributed him.

Really?