I haven’t tried this… But according to the Microsoft instructions about field switches (http://office.microsoft.com/en-us/word-help/insert-and-format-field-codes-HA010338798.aspx), you can add text to a field code. The text must be in single quote marks, and displays as a constant for the field. The examples on that web page show the text at the end of the field, but you could try it earlier in the field by testing putting ‘120/’ in front of where the SEQ number will go.
LION also carries a heavy-duty, 6 wheel automatic numbering machine with rubber faced wheels. The rubber wheels work great for metal marking and plastic marking when used with LION fast dry ink. As with the other LION numbering machines, this machine is made in Japan with precision crafted one-piece hardened steel frame with all metal interior construction. LION machines will provide years of reliable use. Ideal for sequential numbering operations to use as a date and number stamp, serial number stamp, an inspection stamp and etc. sequential numbering in publisher