extra plumbing in head and washers

[Zetomagneto]

Hi all,
 
I've recently come in to possession of a new head that is different to any I've seen before.  Along with the spark plug tapping there is an extra tapping in to each cylinder, I understand that these were done to facilitate the addition of a little extra fuel in to each pot during cold starting.  In my case each of the 4 holes have been plugged with a nice brass washer complete with an odd “sandwich washer”.  The washer has copper on both faces and something in between, see attached photograph.
 
A few questions;
 
1)   Does anyone have a photo of one of these heads set up with the taps to allow the extra fuel addition?
 
2)   Can anyone advise what this type of washer would be called and what material is sandwiched between the copper?
 
3)   Unless I can find something better I though the existing washers could be replaced by copper crush washers, thoughts?

They are copper/aspestos, you can get new ones from the VAR spares, Steve Newton is the Man