The evidence is twofold. First is the length of the instrument: Molaro and Selvelli estimate that the extended instrument would be some 180 cm or so long. Keplerian designs are longer than the earlier Galilean designs (a misnomer, since Galileo did not invent them). Second is the size of the eyepiece, which appears to limit how close the eye can get to the eyepiece lens. That would only make sense in a Keplerian design.
The question then is who built this telescope, and what was it used for. Keplerian designs can achieve much higher magnifications than their Galilean cousins. That would have given its owner a significant advantage over anyone else scanning the heavens... If they'd troubled to look, that is.
Raising the question:
...Could it be that the owner of one of the most powerful telescopes on the planet failed to point it skywards? And in failing to do so, missed a chance at the kind of scientific immortality that Galileo was later to achieve?