Hello BoardAndBrush and welcome to the business forums.
Thanks for your question on how to tell the difference between forwarded calls from your business and personal calls. I can definitely understand needing to know what tone you would need to use.
You would need to set up a feature called Distinctive Ring. Distinctive Ring allows you to provide a unique ring or call waiting tone for incoming calls by setting rules for the incoming call based on the phone number, time of day or day of the week.