5 will get you 10

[GEORGE THOMPSON]

        Here is an expression that's very familiar to me as a way of
expressing confidence in the truth of a statement, yet I don't find
in in RHHDAS nor in several other likely sources, and I have nothing
in my own notes other that this, from last year:

Five will get you 10 that by now most of you can't even remember who
shot J. R.  New York Times, May 12, 1998, p. B1, col. 1

        I can't even remember when I first heard it.

        Any comments?

George A. Thompson