Date check quandry: Factory m30 to m20 conversion?

[Napier]

I did a date check on my frame number which came back with 2 separate records:
1958 m30 CSR
1959 m20 CSR.
My engine is a 59 CSR which ties in with the later entry.

Is it possible that an unsold m30 would go back to the factory when the m31 model came out in 59 and be reengined to m20 and sold to a dealer again as a m20? Any other theories on what this could mean and is it common?

Many thanks in advance for your help.
Hugh

[clive]

I would make contact with John Tinley at dating@jampot.com and see if he can clarify from the clubs factory records. Explain the two date checks you have done, i assume on the club system, and its come back with two entries.

[Napier]

Thanks for the advise Clive. I have done just that!!

[clive]

Just as a follow up to this question. When I bought my (first) 1958 G11CS, equivalent of model 30, it was in pieces and missing any registration documents. It had clearly passed through a number of hands given the names and addresses on the boxed refurbished parts on its way to partial restoration when I got it. When I came to register it my original application to do so was rejected as DVLA as they said it was already on their books. Instead I had to apply under the lost documents scheme. I eventually got the V5 with just the one previous owner showing. Club records showed it was sold to a dealer in North Wales. So I thought maybe the owner was using it in scrambles but internet searches should up no results.
A recent Facebook nnentry claimed most of the G11CS he had seen actually in the USA were the 1958 one year only G12s. The US market was always keen on bigger "cubes".
I have been left wondering if my bike was sold at a reduced price to clear to be used on an upland farm.
I will be interested to hear the outcome of the dating search.