Need help with an Id on an Enfield Pistol with elevated rear sights

I hope the pics made it: I bought a large gun collection from a widow and this Enfield revolver was is in it. It has an unusual rear sight that is fairly well done and I cannot identify the gun, so i would appreciate some help.
Of course I hope it makes the pistol "rare and valuable", but i am also prepared for "screwed with and cheap", but in any case i would appreciate ideas on value.

Markings:
matching numbers 5206 on barrel and frame, spt50 on cylinder, BNP with crown, .38, 3 1/2, .767, and "tons" all in one grouping on frame in front of cylinder, on frame behind trigger in "ENGLAND" and BNP with crown again, ZF5206 on cylinder, and more.. I have cussed some guns (japanese type I rifle for instance) for having no markings, but this enfield pistol has enough for several long guns.
thanks for any ideas. Gun seems to function well, very worn with little finish but I would shoot it in a heartbeat as it seems very solid. thanks!

Attachment 14666Attachment 14667Attachment 14668

Oh Yeah, the rear sight is decently done but I believe it was welded on after the gun was built, after close examination, and not part of the original machining. grind marks are visible where the weld was smoothed, I believe.

Although your pictures are such poor quality it's hard to tell, most likely 'somebody' took exception to the difference between POI and POA which is common with these guns especially with commercial loads. The proper course would have been a higher front sight, and I've made one for myself in the distant past. Enfields this late in the production run often bore little identification beyond th entwined E and D logo and a I* (or I**) on the right of the body, and the barrel date, thus: '43. Serials were prefixed with a letter, which ran all through the alphabet and began again at ZA, getting at least as far as ZJ.
The usual British commercial proof marks are present, applied after it was sold off.