Oz:
Nice looking Hollis. I have two Hollis guns. Both are 12ga SxS. One a nice pigeon boxlock and the other a light sporting hammer gun. I just bought a pretty decent MH .577/.450 sporter with the express sights.
I is definitely a working gun, and is said to be from South Africa. Plain action, browned barrel. Loop and hook barrel mounted sling eyes. No maker is identified, but the serial number on the barrel begins with WR then numbers. Of course there are the number of proofs. The express sights are like yours, One standing for 100 yrd, 4 folding up to 500 and then the ladder type that goes to 1100 yrds. All with Silver line insert. Front sight is a simple blade, but may have had some insert at one time. The bore is, I would say, good to very good. Slight pit here or there. I bought a box of USA made Jamison brassed TenX cartridges. The gun won't close on the loaded round. I see the chamber has a rather abrupt shoulder more in the style of early .577/.450 cartridges I have seen. The TenX have a more sloped shoulder. It is a very small fraction of a difference, but I will need to make some adjustment to the loaded rounds to have them work. I haven't yet shot the rifle, but so look forward to. This makes my number three Martini Henry. I have an Australian Cadet in .310, another large frame M/H that was a .303 carbine, but I rebored and had the chamber opened to a close copy of the .375 Express 2 1/2. I have shot the Cadet, but not yet the other two. I made up cases for the .375, but have had no time to sit an work up the loads. Soon, I hope.
Here are some photos.