27.0 *tends* to indicate something other than Columbus SL or SLX (typically 27.2), it's a size associated with Columbus Cromor, among others (including lots of Tange-tubed bikes, which this would not be, and some straight-gauge). Aelle usually is 26.8, but there are many exceptions to these generalities. Best thing would be to weigh the bare frame and compare to something of the same size built from a known tubeset. In any case, I doubt that you'll notice a lot of difference in the ride quality of a well-built frame made from one of the "lesser" tubesets, and that's what counts if you're keeping it to ride.
edit: to Belgium and EastGermany add Oslo, Norway since there's a really pretty Norwegian Diamant "ladies City bike" in a current thread...completely different company, though, but the same name.