With just the 3 Melbourne teams winning this week, I can't imagine that's happened to often?
Also happened in rounds 6, 7 & 11 this year (counting Geelong as a 'Melbourne' team).
last time two Victorian winners - R9 2014 (split round)
last time two Victorian winners in non-split round - R15 2005
one Victorian winner - R3 1916 (two matches, one drawn)