These carbs are a carbon pirate copy of AMALs but I should be surprised if there was a valid copyright on them 50 years after they were first produced. F.e. I know that all Norton rotary engine patents have expired by now, stemming from the same era.
The only protection there is is the "Amal" trademark. That is explicitly not used on these copies and, if you read the sales blurp, the word "Amal" is carefully left out, and they are referred to as "OE" carbs.
I should think the copies come from the Far East and, personally, would not use them on my own Nortons, or sell them to customers as long as the original still exists and is of good quality.
Pirating of AMAL components has been going on for quite a while, with jets etc. available for a fraction of the real thing (and a fraction of the accuracy.....), and I know at least two high-profile exponents on the Norton spares front whose main concern is purchase price, forget quality considerations, who no doubt handled the pirate Amal copy stuff and will now handle the pirate carbs.
Rest asured Andover Norton will stick to AMAL genuine spares and carbs even though Wassell's sales blurp was correct in critizising various points about the business conduct of AMAL's current manufacturing company towards their dealers cand distributors, points I have put in writing to the same company before and, using Wassell's blurp as confirmation of my findings, again.
Joe/Andover Norton