Sorry about the pics, they were taken with a flash. The hardware looks all very original, very flush and expertly recessed. The photo is of the back of the door which is also very attractively, though plainly, carved , possibly another sign of reasonable quality.
Other than the replacement shelves (2 not 1) there is no sign of any restoration, and although in the flashlight the shelves look bright spankers I would say that they do have some age to them, at least 40 - 50 years. I've mounted it temporarily, hence the new screws.
I'm fairly confident, as I can be, about its age, it's just the decoration on the door that puzzles me. I've seen a lot of corner cupboards over the years, both Victorian and Edwardian, but nothing as ornate as this. It's ornateness is reminiscent of something from the East (Near, Middle, Far) but the design certainly isn't.