Yeah, I tend to agree, the one pictured is not really anything special, once you get to that era, you tend to find that many collectors are not interested as they focus on machines predating the 70's.
For those collectors who do retain intrest in the 70's, (such as myself) there is few who want much to do with the 'By Victa' mowers, and on top of that, many 70's collectors are more focused on the 1970-1974 period in which Victa used the alloy G3 carburettor.
That mower would be from somwhere 1975-1976 i would guess, at oldest it's a late 74, and with the carby backwards i cant see it being newer than 76.
It's a standard mid 70's Victa Series 70 MKIV engine, with a G4 carby, the set up is pretty low end, and is not really important to any stage in Vict's development.
Myself, I would not buy this one at any price, as a collector I dont want it, and I'm set for mowing the lawn.
Around here, you would also have a little trouble pulling that much for a sale to somone who was after a machine for cutting the grass, I tend to find anything pre-1983 hard to get more than $80 for.
