I found a few of these under some of the value springs. http://www.users.bigpond.net.au/drekkus/

It says on the top "This Side Against Valve Springs"

Valve stem seals.. or oil seals..

They're metal and were under the valve spring.They were also only under 4 , 3 exhaust and 1 inlet.They almost look like some sort of shim but I can't find anything in my parts book that look anything like them.
I'm trying to work out if I need to put them back on or not.

They are valve shims, used to pack the springs up. Used by engine builders to get more valve spring pressure, by compressing the springs to their designed set length.
Maybe those valves where these fitted are sunk further into the head...

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

and you need to be careful when you put the rocker gear back on if the shims have slipped out to one side from under the spring retainer. The post can foul the shim as you are dropping it down

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"Show me the Mini!"