Thanks Diddy and Nick
I'm actually in NSW, Australia, and our death indexes are available up to 1978. I've also checked several other states, and will be doing more this morning, but I think there was a marriage separation, so he might have died under another name. I've checked every known variation of his name, and also under parents' names (an advantage of our indexes) - no go.
There's a big gathering of the extended family coming up in March, and the friend I'm helping will ask then - possibly our only real hope for a clue.
Thanks for your input
Annette
