Help needed Old Wassily chair  

Hi , I know there's 1000s of these things around with a few authentic oddities mixed in .I have an aged example dating from 1960 to 1970 approx .It came  from the estate  of an architect collector who passed away aling with lots of high end authentic mid century furniture.The chair has  thick double stitched saddle leather with stitching all around frame loops and  internal  material inserts where straps connect to frame.Correct small grub Allen screws where frames meet , dates from 1960 to 1970 approx.Remains of  small rectangular lable on underside of seat base .Everything is right.Really good  heavy quality item  .But,It has end caps .I just don't get it. Can anyone offer advice. Is this a later Thonet or Stendig  perhaps ?.Did Knoll at any time produce a limited number with chrome metal end caps ? It's not the normal knock off because of age , quality and tbe person who owned it .He would only have the best .

Thanks 

Barry