Interesing ... more information comes to light!
I was searching American auction sites and "borrowed" this text:
"Harrison Brothers are also known as Harrison Bros. and Howson. The company were based at Norfolk Street in Sheffield and are known to have been in business from 1853 to the 1920's, although it is very possible that their dates extend beyond this period. They had an office in San Francisco to take advantage of the gold rush and were patronized by the Queen."
And on
www.antiquesilverspoons.co.uk
"Harrison Brothers & Howson
Marks used:- HH, HB&H
Trademark:- a five point crown
Originally known as Harrison Brothers (from 1849) this Sheffield manufacturer took on Howson as a partner in 1862. The majority of flatware produced by them was EPNS, however some silver items can be found. They also produced good quality cased sets of carvers, fruit eaters and fish eater/server sets. They still trade today."
There is more out there
Roger