The IRS Pocket Commision states:

"Pocket commissions will be issued only to those employees who are required to present proof of their authority in the performance of their official duties. With the exception of their use by Inspection, pocket commissions are primarily intended to identify Service personnel to the public when dealing with tax matters."

But who does have real authority?

Download the PDF document

Or read directly from the IRS manual:

https://www.irs.gov/irm/part10/irm_10-002-006
http://www.irs.gov/firm/part1/ch13s06.html
http://www.fda.gov/opaccom/laws/adminpro.html

You can also read the thoughts of Sherry Jackson, former IRS agent.