"DAITO" fire damper

[DuctIAQ]

I am in the process of performing a fire damper inspection for a client and have come across a damper that I have never seen before. It is a blade style fire damper with no visible fusible link. Mounted on the outside of the duct, on the damper blade pivot rod, is an arm with a weight on the end, that appears to be designed to help close the damper. The word "DAITO" is cast onto the weight. On the opposing side of the pivot rod and weighted arm there is a "nipple" protruding from the side of the duct that is engaged to keep the weighted arm up (and the damper open). I believe the damper may be activated when heat in the duct affects the "nipple", causing it to retract and allowing the weighted arm to drop , which causes the damper blade to rotate and close.

Is this anywhere near being a correct scenario? I need to know how this damper operates so that I can test the damper per code requirements. I can't find any info on the web regarding this type of damper. Any help would be greatly appreciated.

Thank you.