Qianlong Tongbao coin - what mint please?

What I have may be a Qianlong Tongbao coin (N#1133), but I cannot read the Manchu script on the right hand pic - can anyone assist in identifying what the right hand character on the right hand pic is, please?  Thank you. Weight 4.2g according to my digital scales.

N#36378 

 That is the first result in putting the second picture in the Search 

Reverse
Two Manchu words (read vertically) separated by the hole.

Script: Mongolian / Manchu

Lettering: ᠪᠣᠣ ᡤᡠᡳ

Translation: Boo-gui 

 Putting the picture in the Catalog tab above > https://en.numista.com/catalogue/index.php?r=&st=147-150-149&cat=y&im1=684e4d3715345.jpg&im2=&ru=&ie=&ca=3&no=&v=&a=&dg=&i=&b=&m=&f=32&t=&t2=&w=&mt=&u=&g=&c=&wi=&sw= 

Thank you very much for helping me identify it.  Now, should I clean the coin or do something about the slightly green patch? Or am I mistaken in thinking it might have bronze disease?