The SCSW 4th edition doesn't list the TVU prefix for any of the known dates, but there is a TVC group located in 1991 and TZS, TZU, and TZV listed for 1993, so I would extrapolate yours falls somewhere in the first couple of years of the 1990s. Hope this helps. BTW, is yours a "plain" 5903 or does it have a model suffix like SSV or TSW?