was an option in all countries for all H2 and later H1.
When you ordered a brand new H2 on the seventies you could ask your dealer who ordered the twin disc option and you could also order one after for a used bike.
But there was no statistic excepted if you could know how many kits were ordered in a country.
WS Churchill "You were given the choice between war and dishonor. You chose dishonor, and you will have war"
theres quite a lot of twin disc conversions, its a better option and makes a world of difference to the stopping power, can get a r/h standard caliper professionally converted for about £45,...