With the gun in the condition as shown in the first photo, hold it up to the light and give a solid push on the Hammer. If the Hammer goes forward (you will be able to see how far by the light coming in between the Cylinder and Standing Breech) far enough to strike a Primer, then the gun has NOT been retrofitted. If loaded, it will fire if you hit the Hammer.
If the gun HAS been retrofitted with the proper Hammer-block, then the Hammer will NOT go forward to strike a primer UNLESS the Trigger has been pulled back all the way. Normally, they are quite solid until the Trigger is pulled; anything else is a trip to the Gunsmith or else, in the case of the Enfield, crowing from the rooftops.
There are actually a lot of guns without Hammer-block safeties built into them; the original Colt Single Action Army is one of them, which is why some of the old-timers carried them loaded with 5 only. In a civilian situation, it takes only a bit of interest and some common-sense and things are pretty safe. The situation is entirely different in the military, in Wartime, with a Draft, when you are taking completely uninterested city people out of their cozy offices, handing them crude contraptions such as Sten Guns and expecting them to be more dangerous to the other side than they are to their own.
I think a LOT of collectors would welcome the opportunity to have an UNaltered Mark 1**, if for no other reason than to fill in a "set".
Enfield revolver parts ARE available in the US. Just send them to a pen-pal in Iceland and have him re-send them to you. The US has an agreement that allows Icelanders to purchase these parts, but they have never made the same agreement with Canada. I think we should just shut off the oil until they come to their senses..... take about 12 minutes. The parts will enter Canada FROM Iceland with no troubles: just pay the GST.
Funny world we live in......
Hope this helps.