Hello IRB and Joe

I think Joe is pretty close, but there is a devil here - in the detail.
The model 16 on the engine plate is a Victa reference, not a Kirby one.

The general trend I have observed in 1960s Victas at the first tier is this:
the 160 Corvette was the flagship; the 125 Cortina the first option below this.
Whenever the Corvette's base was updated, the Cortina would receive the
older Corvette base.

So, is this a Corvette 4 from 63-64 (V21), or a Cortina 4 from 64-66?
Joe has identified the cowling as the critical issue. I totally agree.
The corvette was up-speced to have better badging and chrome - to differentiate
it on the showroom floor.

Here is the Model 16 4-stroke in Cortina and Corvette configurations.
Note that the Cortina does not have the front name plate, or the
dress piece round the trip-release impulse starter.

[Linked Image]

IRB, I note that your first photo appears to show lugs on the front
of the cowl - suggesting it originally had a name plate.
Could you confirm that, please?

[Linked Image]

I can only conclude that this machine is a V21 Corvette 4 from
the 1964 Victa range (1963-64).

I hope that is a fair dating assessment.
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Jack