Looking at the
parts list for the 409, the exhaust didn't have any resonators fitted in the front pipes.
I have attached a photo below of a resonator from my 411. It's a straight through design but the inside wall is perforated. It's very heavy for it's size and I suspect it is a "glasspack" resonator.
I'm not sure whether these were fitted to the 411 originally. The resonator body itself is handmade and there is no sign of rust so it is probably stainless steel.