Originally Posted by
stapfam
Frame size using the seat tube length can be open to errors and the same with top tube length.
If you get onto the Spec sheet on line for your bike and look at Geometry- there is one measurement that can confirm the frame size and that is Head Tube length. Top to bottom length and then transpose to Frame size and you can tell what frame size you have.
That's what I was thinking too. Looking at the photograph that looks to me like a head tube for a 58 cm frame. The seat to handlebar drop isn't as extreme as is commonly seen today either.
Does it matter? How does the bike feel when you ride it? It might be one of those things that's like Chinese food - if you like it, don't ask what it is.