OWK’s stable - De Rosa / Geoffrey Butler / Ridley Oval

chainring arrived yesterday safe and sound, cheers
cool, thx for letting me know

How far down the tube are you getting a 27.2mm reading?

Only until the start of the 27.4mm section, that's the way the tool is designed; tapered to only measure the first part of the seattube, confirming that the clamp area is 27.2mm unless...

Could it be that the tube has previously been reamed from 27.0mm to 27.2mm, but only 50mm down?
unless this is true, in which case I will need a 27mm post to confirm...