I'm thinking it has been made during the republic period . The quality of the decorations is stunning. I consider buying it.
It is a Jiaqing mark. Could possibly be genuine as vases of that period & style were made but I've no idea if it is or not. Hard to tell from the pics whether it's machine-made or not & a perfect circle which would make it modern.
As a guess, I would go with 20th c repro of a Jiaqing piece. Glaze seems slightly /too/ perfect. Nice quality, though.
It is a very nice, high quality vase but the mark looks like someone really tried to copy it but just could not get it right, I have seen similar vase coming from China same Quality, looks new to me.