It not only looks like a genuine Suzuki part, it has a Suzuki part # 61100-41870-019 REAR SWINGING ARM SET. November 1976
If it is deemed illegal surely these optional part numbers published November 1976 are also illegal :
09825-00002 LEVER, tire
09821-00004 INFLATOR, air
09826-00001. TOOL, tube repairing
99000-33010 GASKET, liquid
99000-32040. CEMENT, thread
99000-25030. GREASE, super
99000-10105-019. PAINT. ( BLACK )
99000-10105-163. PAINT ( PHLOLINA. YELLOW )
11400-41811. GASKET SET
11400-41850. GASKET SET
11400-41891. GASKET SET
After typing this out I thought why not order these optional parts from Suzuki and if any or all of them are available or were available Pre 78 and seeing as they are out of the same parts catalogue as the alloy arm then surely the arm was available for sale as well. I have been informed by MA that a eligible part only has to be available for purchase, not necessarily purchased.