I think I can only weigh in on the stock, the rest I'll leave to more advanced Enfield people: I've never heard of anything other than linseed oilicon being used to treat Enfield stocks, except sometimes grease on the inside of rifles for the purpose of storage (For the purpose of the metal components but I suppose some always gets on the stocks). I have seen plenty of rifles with very very very dark wood furniture, I can only assume it is from the grease, grime, sweat, and who knows what else that these rifles have been covered in in the last half century or more. I did clean up one old stock that was somewhat chocolatey like you describe with water, rags, and a toothbrush and after oiling it came back a very nice red. Also have two rifles that were a dusty black with some kind of dried up substance on them. No choice but to sand them back just the tiniest bit to get the solid gunky stuff off. In your case if you can still the wood with no kind of finish I'd say its what it is supposed look like. Enjoy your new rifle.