Let's hope the 130mm OLN is by design. 'Spreading' aluminium rear triangle would not end well.
I have looked at my down tube. It's got brazed on 'squares' which allow the Campagnolo friction levers to be screwed on.
I guess bar ends are the only valid assumption.
Wrt frame size: my 58x59 is immediately below the seat tube lug. Your 3-53 assumption makes eminent sense. I will look (for interest) at my steerer tube the next time it's out.
What are the wheels (hubs/rims)? Mine are Maillard Atom hubs laced to Weinmann rims.
Wheels are a real mixture a more modern Quando front hub and a rigida rim whilst the rear is a an old campagnola hub with a rather bent axle on an omega rim wheel .
I am unsure re what wheels i will use tempted to put a set of light hybrid one i have kicking around and then i might be able to use up one of the sets of marathons i have laying around if there is enough room
I cant see anything odd or out of shape on rear triangle other than it not having a hanger for the mechanism but it doesn't look like it's been cut off ??
Does yours have the the thin metal strips on the inside face of the rear drop outs ?