How do we know that this decree was written by Cixi?

Question

In another, extremely helpful answer we found the handwritten text underlying many claims about Empress Dowager Cixi’s illiteracy (see aforementioned answer for example of such claim). But how do we know, this is actually written in Cixi’s own hand?

TLDR

There are also very beautiful calligraphies attributed to Cixi, such as the following one (found here) bearing a seal „慈禧皇太后御筆“. My goal is to find out whether one of the documents is falsely attributed. It is also conceivable that her writing was bad in 1865, but very good around 1903, when Katherine Carl and others described her as highly skilled with the large brush.