I still haven't found out if Alfred Hollis built his own guns/rifles but I'm not giving up!!!
As I said on 40X's other thread, that isn't much of a mystery. I've owned an A. Hollis & Son nitro double rifle for 20+ years and so have always paid attention to the guns bearing that name, and have been researching the British "makers to the trade" for some years as well. Geoffrey Boothroyd and I kicked around A. Hollis & Son a fair bit many years ago, and additional information I've gotten since then has only confirmed what he thought at the time.
Yes, there's no question that Alfred and Isaac were cousins. Boothroyd was quite certain that there was no connection between the firms though. It's clear enough that their guns didn't come from the same source. The A. Hollis guns are generally of a higher standard than those of I. Hollis.
There can be no question than A. Hollis marketed himself as an express rifle specialist, especially double rifles. A. Hollis express rifles are fairly common, and their smoothbores unusual. Between myself and three friends, there are four A. Hollis & Son double rifles in my hometown alone, and I can think of where four or five are listed for sale right now. I've seen a small handful of their shotguns and ball and shot pieces listed over the last 20 years, but have never had one in my hands.
I don't know if Alfred ever made any of his own guns or not - a number of successful, well respected names did not. By the nitro era, he was certainly primarily a retailer. Identification of the true maker of a retailed gun is sometimes impossible, and sometimes so simple that it's impossible to make a mistake. The latter is usually the case with A. Hollis double rifles. I've seen only one that wasn't from Harry Leonard. The .500 in the link above, No. 15056, is a typical Leonard built Hollis. It is of almost identical appearance to a Jeffery of the same vintage because Leonard was building most of Jeffery's DRs then also. Leonard's serial number was stamped on the lower rib about .75" in front of the loop. I didn't see that gun in time to check the number before the auction. Given the Hollis serial number (I think this gun is from 1905-1906), Leonard's would have been in the high three to low four digit range. The .470 for sale at Cabela's is strange. It's certainly not from Leonard, and the serial number is not A. Hollis & Son's.
A. Hollis & Son disappeared from the directories in 1919, and probably ceased to trade during WWI. I've never seen one of their guns with the date code stamp introduced in 1921, or the chamber length stamp introduced in 1925. The highest number gun in my notes is No. 15153, a .470 bearing Leonard number 1962, from 1915. Holland & Holland currently has this rifle for sale.
I can't speak for who made A. Hollis & Son's shotguns, as I've never had one in front of me. Sherman Bell had a ball & shot piece in a DGJ article a while back that looked like Scott.