read.S can read the binary files produced in some older
  versions of S-PLUS on either Windows (versions 3.x, 4.x, 2000) or Unix
  (version 3.x with 4 byte integers).  It automatically detects whether
  the file was produced on a big- or little-endian machine and adapts
  itself accordingly.
data.restore can read a similar range of files produced by
  data.dump and for newer versions of S-PLUS, those from
  data.dump(....., oldStyle=TRUE).
Not all S3 objects can be handled in the current version.  The most
  frequently encountered exceptions are functions and expressions; you
  will also have trouble with objects that contain model formulas.  In
  particular, comments will be lost from function bodies, and the
  argument lists of functions will often be changed.