well, I am not sure that Mike Walker co-owner-founder of the company ever compiled a list of serial numbers matching it to production years but I am in no doubt that he has the data.
I am not quite sure what you would want to establish with the serial number , these are modern saxophones, produced for this English reseller company and under their specifications in China, or, for the M2 series, in Taiwan and rebranded BW.
They ideally undergo QC in the UK prior to be sold. Palo Tung of just saxes has been know to be a distributor in the US for these saxophones (he may be able to offer some help with dating).
The BW company started selling these saxophones a decade or so ago so any horn cannot be older than that ( they were originally branded only Walstein which was a brand made up by the combination of two surnames by Mr. Michael Walker and his partner Ms. Harriet Grünstein).
The name changed to Bauhaus Walstein because of some trademark registration issues (there was another Walstein brand somewhere).
Your best bet is to get in touch directly and ask.
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