We have just purchased a pair of 1930s/40s from the Glee Club in Nottingham. They are currently in 'restorable' condiition !
It's an advantage to start the restoration with the chairs in original condition (rather than having been reupholstered once or twice before) so we can copy and enhance exactly how they were intended to be. That would include the internal springing, cushion content etc as well as the leather upholstery.
Of course, the prospective new owners can opt to make suitable changes to their own taste, a different leather tone being the obvious example, or, with these chairs, the introduction of contrast piping would be very attractive - see the image of a similar restoration of a pair of (non-'tache) French chairs in the photo gallery showing exactly that.