Hello, I am from Dumbarton and I don't know of a "New Street" could it have been Quay Street? it could maybe be why the West Dumbartonshire Council have no record of his death? I'd double check the address.
Did you find it on Ancestry or Scotlands People? Ancestory for the most part needs to be taken with a pinch of salt.
The Denny family have a family vault/lair in Dumbarton Cementary.
If you call Dumbarton Libary they have a name index of death notices published in the Lennox Herald,the local newspaper. They may be able to help shine a light.
Apologies,if my reply sounds condesending, not my intention at all, just wanting to help a little if I can. Hope it all goes well
