Anyone know for sure who made these headsets?
 I have heard "Bardon" but I'm not at all sure.

 This one in the pictures was purchased from
 the Jack Taylor shop in England.

 Lots of French tandems used the 28 mm steerer, as
 well as the Taylors and a very small number of USA
 custom frames (e.g. late-70s, early-80s Rodriguez).

 Important note, this headset will NOT fit modern 
 "OS" 1-1/8" steerers, and a modern 1-1/8" headset
 won't fit on a 28 mm steerer.   1-1/8" = 28.6 mm,
 which is definitely too far away from 28.0 mm

 I also have a Stronglight in this same "oversized"
 dimension and it is clearly different (& better), 
 i.e. this one here is probably not a Stronglight.

 Note the chrome-plating on the races -- better 
 headsets (Campy, Stronglight et al.) either mask
 the races so they are not chromed, or grind after
 plating (I'm not sure which).  Chrome on the races
 eventually flakes off, leaving chrome flakes in
 the bearings -- not good.  They are clearly good 
 enough though -- lots of tandems have used them
 for years, decades even.

 I THINK I remember JT tandems came with better
 quality headsets in the olden days, but I'm not
 at all sure on that.  The Stronglight I have
 definitely seems to be higher quality; did JT ever
 use Stronglight brand?

 I hear these headsets are made to take 5 mm balls,
 not the more-common 5/32" or 3/16".  Haven't tried
 it yet to confirm.