Hi Pete, Dont forget. They were stamped in a time when craftsman ship mattered! & Armourers took thier time & patience with virtualy EVERYTHING they worked on. The Old chap said he stamped one or two replacements that broke during trials. You couldnt tell the difference with his work! Lol! I would ASSUME that the vast majority were done at Enfield or through Donington or the like. before being issued to various theatre units for the trials proper. He said there were TWO variants of the 'New' Rifle on trial. One had a small Optic sight that YOU would know about. ALL the Trials Bayonets were released & sold off in the Seventies through Wallis & Wallis of Lewes, UK. We KNOW this for a fact, as the old boy was Fireams Cataloger & Manager with them before he set up his own shop. He obtained a couple through wallis's & still has them in his collection. There are a few floating about at the moment at Militaria fairs, buth the dealers want STUPID money for them! Personaly, I would stamp one upo myself to fill a gap! At what they are asking for them, you could buy four different decent bayonets!
I believe the number after the EX was the rifle number.