Mantra API: How to point to a specific TMS instance if username and password are the same on both TMS instances linked to Mantra?

We have a question about the Mantra API and using a system account for the connection.

We have developed a connection to the Mantra API and created a system account specific to the connector. However, since Mantra is a cloud solution that links back to our TMS instances (we have two; staging and production) depending on the login credentials; how do we determine if a job is created on production or staging if the system account & password are the same? While I can create different accounts on each server, these are often synchronized and eventually, they will be the same again. 

I have heard that there is an undocumented way to do this. Can we get documentation (an example) of how to point to a specific TMS instance using the Mantra API?