Hello Stuart,
You certainly test the memory!! I'm afraid I can give little further information to what I listed in my initial post. I recall the chap that I purchased it from was not sure if William was Australian or English. He knew enough to be certain the box was made in Changi. I can no longer remember why this even came up at the sale and don't recall there was a relationship between William and the salesman, though I very much doubt family would relinquish such a piece of their history. There's something in the back of my mind that William had no family...but I can't be sure anymore. The sale was in Lake Macquarie, New South Wales, Australia.
I started searching on a William Benyon Boyes that died in NSW in April 2009 as it may have fit with an estate sale, however I never confirmed if he was ever in Changi.
The box is now long gone, given as a gift.....with the history as known at the time included.
Kind regards,
Jeff