The whole world is looking for a Grant like this and you are the one that have it Dave!!! lol
That is the second batch of Grants. The first batch had an electronic switch on it and it was the first GG ever made.
Your Grant doesnt accept the new GGTB button because the hole of the tube where the button rests has no
threads buddy, I am very sorry. But I took back all those Grants 4 years before because they were producing a short if you touch the body and the button at the same time with a metal object. You may be the only person that has a Grant like this!