Mark, I gave that head and barrel to Brian, it was off a Matador 200 m4, I bought a 200cc m4 complete engine from the states, as i was going to use in a sherpa T frame which I bought off a fellow in wagga, when I got the frame it was the wrong model and m4 - 4 speed engine was on its way to me, the engine was no use to me when it arrived and Brian bought it off me, the head on the m4 engine had broken fins. so I gave brian the head and barrel to suit.
So in saying all that, brian may also had a spare radial head too. Years ago when I was working with Ray Ryan I did import a genuine Metisse from States 1998, and it had a radial fin head, Bernard Andrivon ended up with that metisse, and later sold it to Brian , so brian may have keeped that head when he sold the bike to another fellow who restored it (I think), because at the time, the bultaco was not eligible for pre65.
There was a bum fight over the eligibility rules for Bultaco metisse.