Pick

This is the kind of coin used by Brian all over his carreer to play the Red Special guitar.
Probably Brian is the only musician in the world (apart his mayniacs fans) to use a coin like a guitar plectrum.
As regards the way to play guitar with the six pence I think that only Brian can explain it best.

"It's a great help to use the coin as, depending how it's orientated to the strings, it can produce a varying amount of additional articulation, and by that I mean when you can hear just one string peeping through the whole spectrum of the rest of it.
So, if the six pence is turned parallel to the strings, it's quite a soft effect, even though it's a piece of metal.
And if you turn it sideways, the serrated edge changes the sound quite dramatically.
I've always preferred the coin to anything else both for that reason and because it doesn't 'give' between the string and your fingers.
Sixpences are very cheap these days!"

Believe me, there will no metal plectrums giving to you the sound of a sixpence coin.
By the way if you don't have the possibility to have it, you can search for a similar coin.
For example the Australian 5 pence it's the same as the English six pence.
Or if you are a very luky person you can find the six pence piece made for Brian by the Royal Mint in 1993 and sold during his "Back to the light tour".
Otherwise if you live in a country joining the Economic European Union (i.e. all the European states except United Kingdom), you can use a 10 CENT coin.
It has a beautiful gold colour and the same diameter of the sixpence, but it is thicker and the edge is not very serrated.