It does have "not for road use" embossed on it. I keep meaning to polish it off.
Normally that's the main one for an MOT failure if it's actually written on it.
My Quill exhaust is a race can but it doesn't say 'not for road use' anywhere and it's not too loud at tick over either so gets through okay.
Oddly enough i got an advisory once for noise on my Moto GP can which is totally legal when baffled, but he didn't spot the markings on it.
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