Yes mate, that number seems pretty low, but given the high production runs for that model in such a short time, I would assume turnover was also quite rapid. I think it would be fair to assume that mower spent probably no more than 2 months on the shelf between manufacture and sale, giving it a production date around July 56. Its always possible it could be earlier, but what it does confirm is a terminal date for production on that serial number range. The bill of sale does confirm with little doubt, that no Model 2 with a number after 38952 predates a production date of September 56.
I also was thinking about the black plastic wheel ad, and what it suggests. Given that no example of a black plastic wheeled Rotomo has come to light, and that to my knowledge the ad appeared only once in this form, it would suggest that it represents the very first adoption of plastic wheels, at least in concept form. I would interpret it as proof that at the time of this ad (Feb 57), the first attempts at producing plastic wheels were being considered, but the design had not been finalised - hence the colour change. Prototypes had probably been developed and in their rush to generate sales, they had depicted them in the ad in question, before they had been officially adopted. Sounds like aggressive marketing strategy to me.
I think that what the ad does demonstrate is that in all likelyhood, plastic wheels were not introduced until after the appearance of this ad, thus all plastic wheeled Rotomo's, as you've said - #75000 onwards - were produced no earlier than February, 1957.
So, in short, these two terminal dates of production (the bill of sale and the plastic wheel advertisement), by my reckoning, would work out something like this:
1) Serial #38952 onwards produced no later than September 56
2) Serial #75000 onwards produced no earlier than February 57
I guess what would be interesting is to find out how many mowers they were turning out per month during this time...ahh here we go:
By 1958 the company had moved to a new factory at Milperra and its 3000 employees were building 143,000 mowers a year for export to 28 countries.
Aus Dic of Biography
10,000 per month! Damn....
I know all this probably slides previously assumed manufacturing dates forward a little, but the evidence is what it is. Whadaya reckon?
