Only it wasn't. The closest anyone's been able to track down is the IBM Selectric Composer, which was proportional (but with only 4 possible widths) and obviously no kerning. An IBM guy called Howie Carr today and said he was an IBM salesman back in the 70s, and the Composer wasn't used in offices; the market was small print shops. Also, unless they want a suit on their hands, they weren't using Times Roman, because it wasn't licensed to IBM.
I thought I read somewhere this morning (I think it was at National Review--the Kerry Spot) that the font was being used way back even before the 60's (in manufacturing printed materials--or something along those lines), though not available for use in the context that was available to the Guard.