Hmm...Run a poll please.I think what is normally understood these days (and maybe always since its introduction) to be THE Siccama flute is his initial, basic design...
My quasi-probably-non-sanctioned-Sic has those rod thingies, longitudinal and radial/tangential (3rd finger).- a normal 8-key Simple System in most respects, save that it has the better (acoustically) placed 3rd-finger tone-holes with open-standing extension keys to permit their operation by a normal hand. No "typewriter" keys (by which I take it you mean longitudinally mounted rod-axle mechanisms).
Play one for a few hours. You'll find taps will take a bit more effort. If the springs are too light, the keys are more prone to sticking.Properly set up, the springs on the extension keys are supposed to be very light - there really shouldn't be any significant stress or effort (or loss of speed) in using them for taps and rolls once accustomed to them
