While Hellis was in London, I believe all the Chas. Hellis guns I've seen were Birmingham proofed.
As for the Isaac Hollis guns, I've seen a couple and they were crude hammer guns. While I'm sure others will point to exceptions, these were my experiences.
Certainly, a Hellis is worth more than a Hollis, all things being equal.
Hellis is certainly a tier-III maker (tier-II is the likes of Westley Richards, Lang, Atkin, Grant, Lancaster, Hussey, etc.)
Tier III makers would include: Greener, Pape, Egg, Osborne, Turner, Richards of Liverpool, Cogswell and Harrison, Playfair & Bentley, etc.
Naturally, in each class there were several grades and qualities but some firms are known for best guns, others are not.
