The age of Jupiter instruments may be determined by adding one to the first digit of the serial number. The resulting number then would represent the year after 1984 that the instrument was manufactured. For example, if the serial number began with a number "4" you would then add "1" to this number and know that the instrument was manufactured in 1985. If the first number was a "0", would indicate that the instrument was manufactured in 1991. The problem with this system is that Jupiter has been manufacturing instruments for over a decade. As a result, it is not possible to tell if an instrument having the first number "4" was manufactured in 1985 or 1995. Jupiter marketed instruments in countries other than the U.S. prior to 1985, so there can be no real certainty that a Jupiter is not a vintage 1984 or 1985, though it is unlikely.