Thank you. It does seem a mystery. Odd that it has so many authentic-looking aspects except the serial number.Thanks Those are very ‘Orangey’ cable guides re both form and position.
That ‘on the tilt’ position is distinctive - most cheap alloy frames are on top or on side.
That gusset under the downtube is very O2.
And another thing...
The seat tube slot is at the front...again very Orangey and not cheap copy-ey
TBH I'm not sure what I will do about it. I'm obviously not entirely happy, the seller (a bike shop) failed to mention that it had been powder coated or even re-sprayed, when it is quite clear things are not original. They made it clear that they were not sure whether it was a Gringo, but stated it was Series 14 tubing. But as it's been repainted those stickers are not reliable.
Looking back they failed to answer my question about frame numbers too. £135 for a frame that may not even be an Orange seems a lot.