Remember that it came as a bare frame and the OO (original owner) built it up.
I'd assume that it was built for sew-ups or 700c, but there's enough room for the 27x1-1/8's with enough clearance to feel safe.

27's were a reasonable choice back then for somebody willing to sacrifice a little performance for ease of use. I'll be very tempted to lace up some 700 rims as I work it over.

"I have already sent the photos to Verona and I should get a reply within a few days."
Very cool! Thanks!