Can anyone identify my noisy banana exhaust pls?

I've just fitted a banana exhaust that I bought NOS from ebay about a year ago. The seller said it was a genuine Piaggio which I took with a pinch of salt. It's really well built and has RGM 1714/23S stamped on the side. It doesn't have an exhaust stub like the Sitos and Piaggios and was wondering if it's meant to have a baffle fitted as it's incredibly noisy, more so than the Polini that I have just removed. Any help or info would be much appreciated.