Unfortunately, I cannot report anything additional than what has already been said.
Forgeries are made so faithfully that not much can be said about them based on photos alone.
That the patina does not dissolve is a good sign. If you want to be a little more certain, as Lee suggested, you can send a small chip from the shoulder or cutting edge for microscopic examination for inclusions.
However, unfortunately it only says something meaningful if new steel has been used.
X-ray can also provide more clarity, perhaps inscriptions are visible, including, for example info of the construction of the tang to the blade. Furthermore I would still advise to follow the trail of the story, any additional info will help.
best,
|