The bike ended up being 15" and 700mm wheels @uzj100 I am not sure how to translate the 15" downtube, but if anything, it may be small for someone 5'3" vs too large, even with the larger wheels. Misc pics of Trek and Cannondale:
Daughter's old bike. Free.99.
She was about 5' tall and it fit. Could be a lil smaller I think due to sloping top tube.. She is 5'7 now and too small. VERY lightly ridden, but about 7-8 years old. Pretty sure 26" wheel.