The "old-timer" reference work for Australasian tokens is, of course, Andrews. The only two older catalogues worth mentioning are Heyde and Roth, neither of which use such a numbering system. The McFarlane token is not listed in Heyde, and Roth is so rare and unfinished I doubt it would have been used by anyone in the 20th century as a reference book.
There is a more recent catalogue, by Simon Gray (2013) and your token is number 181 in his book. Very close, but not quite, and from your description the 2x2 must pre-date the release of Gray by a decade or so.
On that basis I'd assume it's either a sales number, or a collector's personal catalogue reference number?
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