The physical equivalents of the "DCE-DCE Bridge" probably predate 1978 by many years (RS-232 goes back to 1962), but they wouldn't be so much machines as connector cables.
EIA RS-232-C (1969) "Interface Between Data Terminal Equipment and Data Communication Equipment Employing Serial Binary Data Interchange" - From Wikipedia
Other Possible dates:
RS-232a westernElectric modems
RS-232b DECcommEquipment RS-232b
RS-232cbyte magazine RS-232c
RS-232 Modems or Modems:
The Bell 103A standard was introduced by AT&T in 1962.