those are some good pics, I'd say you have a 531 frame from around '48 to '53 (based on the decal and when the experts say that style was in-use), it's fillet-brazed and I'm going to guess Portuguese (not because of the flag decal on the headtube but the 2-color paint on the stay-caps).
You have a Simplex '599' single lever and I think a "Tour de France" rear derailleur and 4-speed rear (which also fits this approx. era).
The thing I've never seen is that brand saddle: Made in Lusitana? That's unique! Actually, that's Roman...looked it up and that's another clue you have a Portuguese bike since that's a Portuguese (or maybe Spanish) saddle.
Anyway, the oddball stuff includes the SR stem, (maybe bars) new chainring (but it fits the crank!) and not sure about the rims...those could be original but seem newer.
All-in-all a great project: go slow removing stickers and cleaning and you might find more clues...BTW the HS is missing a toothed washer.