What is that “collar” around the neck of my fire extinguisher? I noticed it there after I had it serviced.
This is called the “Verification of Service” collar and is required by NFPA-10. This is a close fitted “collar” that is installed after the “head” or top of the fire extinguisher is removed and service performed. It should fit, as a solid ring; it cannot be installed or removed while the extinguisher is assembled. Information on the collar will tell you when and by whom the service was done; a very useful indicator of service quality.