[G6Tanuki]

As valve manufacture ran down in the 1960s there was a lot of collaboration between the likes of Philips/Mullard/Mazda - basically they would share out the production amongst each others factories. So one manufacturer would do all the EL84s another would do all the ECF82s and another would do all the EF183s, rather than each manufacturer running a dedicated production-line for all the different valves they needed.

Then brand them with whatever brand a particular market was used to.

Hence Made-in-Holland Mullards, made in England Philips, USA-made Brimars and suchlike.

I always thought it deeply ironic that the British Valve Association - an outfit initially set up to enforce 'protectionism' of the UK industry and deter the sale of imported valves - happily went along with having their participating members labelling valves "BVA - Foreign".