From my experience the reason for the size is that it is a far more corrected lens, the field of focus is flat, unlike the summicron. As such it is better at landscapes etc, where you want everything in focus.
However, the price to pay is the size and I'd say it is approx. As big as a Summicron 35 ASPH with the hood on. Last picture shows it on my M4-2, camera is obviously not included.
Exterior wise, there is no mark that I can see of on the lens. Focusing action is sublime, smooth and light. Aperture ring clicks nicely and positively. Clean glass, no marks or other flaws.
The lens tracks accurately on both my M cameras and there are no focus discrepancies. I have included two samples, wide open. Focus on the first image was on the closest tab in the planter. The item "Konica M Hexanon 35mm f/2.0, KM / Leica M mount pristine" is in sale since Saturday, December 21, 2019. This item is in the category "Cameras & Photography\Lenses & Filters\Lenses".The seller is "saviour_s" and is located in Woodstock, Oxfordshire. This item can be shipped worldwide.