Hmmm - delft is still my best guess. It does look like Dolph or Delph.
I guess the next question is - what was his occupation on other censuses?
If he was a merchant, there is a chance that you could find him in directories of the period. I'm not sure what's available for this area.
It might be a good idea to post again on the Dumbartonshire board, BUT make sure you lock the thread and refer to this one, so that we don't get replies on both threads.
It could be that "locals" will have other ideas that might help you.
Kind regards, Arranroots
