Originally Posted by
CV-6
Pull the fork and see if there are any markings on the steerer. Bear in mind that presence of 531 markings on the steerer does not guarantee the frame is 531, but it does increase the odds. Conversely, the absence does not prove it is not 531. It does have some nice features. But I agree with Charles that the brake bridge is "unique" That may well be your identifying feature.
CHeers, I shall do that tonight. I also thought the brake bridge was 'unique'
, it looks to have some thought put into though due to the diamonds on the ends where it joins the seat stay, but then is quite ugly where the brake caliper bolt goes through. I wondered if this was for strength for mudguards or pannier mounts, but then why would it have a fastback seatstay cluster.