Thanks for all your helpful responses. I looked at the carbs but couldn't see the IDTP stamp. I may not have looked in the right place. I attach a picture showing type number and serial number(?) of one of the carbs.
Hopefully it will make sense - if not let me know where to look. Apologies about the photo being upside down I don't know why that has happened.
Again thanks very much for your assistance with this.
Cheers, Neil