Isaac Hollis and Sons, there is very little out there that I could find. I do know that much of what they made was of lower quality (by British standards) for export to South Africa and/or India.

I have a 10g hammer gun with scroll engraving covering the hammers and most of the receiver, more then I would expect for a export gun.

I have become addicted to English hammered shotguns to the detriment of my wallet.