According to this PDF which speaks of making a movie on Kennedy, the rifle was "a gift from visiting dignitaries." I can't find anything else about it.
Still happily answering to the call-sign Peetza.
The problem, as you so eloquently put it, is choice.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.