Thank you very much for that.
It turns out that the Nihon Kensho-kai is a Nichiren buddhist lay organisation, and was only known by that name between 1978 and 1996, so that gives us a rough date for the badge. It also explains the 'ships wheel', my misidentification of the Wheel of the Law ?
Sorry about the images but they were just quick snaps with my mobile, as is the attached one of the reverse of the badge.
Thanks again
Alan