From at least the Ming dynasty there has been a kung fu training method called 金鐘罩 jin zhong zhao or golden bell cover.
The Shaolin Book of Short Strikes has this to say.

If you've mastered the golden bell cover, what is there to fear of spears,
sabers, swords and axes?
若得學成金鐘罩﹐何怕鎗刀並劍戈。

Golden Bell Cover was popular enough to be included in martial novels of the mid to late Qing dynasty, so its existence was no secret.
It was taught to peasants for use in the Boxer Rebellion of 1911 where many unfortunate peasants discovered that Golden Bell Cover does not stop bullets.

What I am trying to discover is if it was taught to small Chinese militias at the beginning of the Qing Dynasty as part of their military training program to take China away from the Manchurian rule.

Are there any other schools that teach or taught or have heard of the Golden Bell Cover?