I'd say it's a '68. It's not unusual for that era Sunns to just have a date and initials scribbled in grease pencil rather than an inspection sticker, and they are easy to miss and sometimes hard to discipher.
There were no "72/73" 200S's. Stick around Mammoth; you might actually
learn something about these old amps...
Also, I don't think it's the "powers that be, around here" that frown on counterfeit badges as much as it's FMIC, the people that
own that logo.
That said; I seriously doubt that
anyone would have any legal or moral issues with somebody recreating a logo plate in order to restore a vintage amp.
Even Rickenbacker, who are notoriously rigorous and aggressive in defending their copyright will provide a factory logo for a resto project.
Provided of course that you can prove that purpose to their satisfaction.