Does this look familiar to anyone?

I got it with the intention of using it but have since come up with another option and need to not just be collecting things... but it should be easier to get rid of if I know what it is.
It came with the standard Lucas L679 gasket, and had the Lucas reflectors (RER 24). So I assume it's original... to something.
I thought at first it was a '68-'70 triumph, but those seem to be shorter - they only extend backward, up the fender toward the seat, a tiny bit beyond the length of the reflectors. This one sticks back another inch or so. I thought maybe it was a BSA but am not sure. It doesn't hook over the grab rail either. Does anyone recognize this?