In the USA, there are a couple of published lists of Royal Enfield and Indian twin cylinder engine numbers. You guys seem to trust these lists in order to date bikes, but this is not reliable. These lists were compiled from the Greenland Mills engine factory records and are often "at odds" with the Redditch parent factory despatch ledgers for complete motorcycles.
As a specific example, these lists state that VA 60004 - 133 are Constellation and VAX 60134 - 345 are Interceptor. This has given rise to a popular (mis)belief as to how many 700cc Interceptors were produced. It would appear this has been calculated by subtracting the lowest VAX number from the highest to come up with a figure of 211.
The Redditch ledgers do not record the prefix letters, but do indicate that there is NOT a definitive split between Constellation and Interceptor at 60133-4. They also record some of the machines with these engines as Super Meteor.
I have photos of 2 engine number stampings in the 602xx area that have VA as the prefix. These are recorded by Redditch as being Constellation and therefore contradict the published listings. They are not the only Constellations in what is supposedly the Interceptor number range.
There are 12 of these VA/VAX engines not accounted for in the Redditch ledgers, but even if all were Interceptor, there still wouldn't be 211 of them.
One of these listings states that 200 Super Meteor and 100 Constellation engines were supplied to Berkeley for use in their microcars. Whilst this may well have been the intention when the engines were built, not all of them went to Berkeley and quite a number of were fitted to motorcycles at Redditch.
I strongly recommend that these listings are used as guide only with caution. The factory ledgers owned the UK Royal Enfield Owners Club are the definitive source for correctly identifying exactly what your UK built Enfield is, and whether the frame / engine are the original pairing.
Whilst we do not have access to the Madras (Chennai) factory records, I have been collecting the numbers from Indian built machines in order that we may date them. There is a "black hole" between mid 1964 and the end of 1968 when we can only make an educated guess. Anything before or after this can definitely be dated.
Graham Scarth
(chairman@royalenfield.org.uk)