I have a London ffst labeled tape originated from the same performance as a Decca blue back record. In fact, I would have sworn it was a Decca till I just pulled it out. It's the Monteux LSO reading of Daphnis et Chloe'. It's on acetate backed tape, bears no dates but is 4 track. Ampex produced all the tapes for London. Perhaps, since they were produced in the USA they might have been legally required to use their US label. Other than Decca, I've never seen an EMI tape either but I do have some Angels.