.../....My 250SL had that clip but my 280 has a different type of cad plated clamp.../...
That's true, the "wrap-around" type clamp shown in your picture was introduced sometime early in 1968; on the M130 engine / 280SL/8 car. That type was used thereafter, until followed by the changed type intake manifold wich had a re-routed, plastic air hose.
I note on the factory M130 engine picture in the early 280SL sales broschure, the black, open clamp is there, for routing of the black braided air hose.
/Hans in Sweden