Stock Office Bank of England

Hi!
This is more of a question for native Londoners. I don't know what the term is referred to.
The Stock Office (Bank of England), historical building made in XVIII cent and demolished afterwards, was it a treasury?
I couldn't find any site on the history of this addition to the Bank of England, and I don't know how to translate it.
It certainly wasn't about modern stocks, since the first stock market was founded afterwards, in 1792 in New York.

Thank you!