@ias, that is a nice pick-up although pretty common I think. If you don't have access to Hartill, then numista.com can be super-useful. For example, using the keywords KANGXI and CASH bring me to multiple examples of your late 17th/early 18th Century cast Cash. I do note that there are likely sub-varieties and the book is probably the best way to chase down that level of detail.
"If you climb a good tree, you get a push." -----Ghanaian proverb
"The danger we all now face is distinguishing between what is authentic and what is performed." -----King Adz