Stanley Gibbon's postal origins

I recently received a very interesting email from Jonathan Hill in Exeter. Although it's known that Stanley Gibbons was from Plymouth, little seems to be known about the origins of his stamp collecting business although it's recorded that his father, William, owned a chemist shop in Treville Street and that Stanley had an interest in stamps from when he was a boy and joined his father's business after the death of his eldest brother. His father encouraged his stamp collecting hobby and a stamp desk was set up within the chemist's shop.
Jonathan's email adds to the story:
'Hello Derek,
I was very interested to read your information about Stanley Gibbons
on your blog (http://plymouthlocalhistory.blogspot.co.uk/2010/05/stanley-gibbons.html).
My father Geoffrey Hill, who was born in Plymouth in 1903, used to tell
me about the family's pawn broker's shop they had in Devonport. I
recall my father's grandfather (my great grandfather) was in partnership in the business with a man called Stanley Gibbons, when one day in the 1870s
a sailor came in through the door and threw a canvas kit bag onto the
counter. It was full of Cape triangular stamps. My great grandfather,
being only interested in jewellery, silver and similar antiques,
wasn't impressed, but Gibbons was. He bought the lot from the sailor,
eventually splitting from the business and going to London to set up
as a stamp dealer. I've never read this anywhere else. I haven't got
immediate access to the family tree (it's in storage somewhere), so I
can't say what my great grandfather's name was. I have no reason to suspect my father made this up and hope that one day I'll find out (and prove)
more! The family were antique dealers and pawn brokers in Plymouth
from Victorian times until the Blitz (where the family shop was totally destroyed!).
Best wishes, Jonathan Hill (Exeter).'