The story of the unknown crankcase assembly is now known. A few newly found remnants have shown up, including the rope plate marked Mercury K4 serial # 1150 and the Eisemann fly wheel magneto assembly which has a small diameter mounting hole. I was concerned that the crankcase extension might have been machined undersize at some point as the magneto plates on hand had large diameter mounting holes and did not fit the crankcase snugly. All in all the bare crankcase assembly has led to a very interesting project, although, not without some learning experiences. Not a complete ready to show and go motor as a few more hours of detail
I know of 6 examples of Mercury K4. I wonder if there are others in club with them and I am also curious as to Mercury K5 model and Wizard WA6 versions. At some point I will write up a long story with all the twists and turns complete with photos and credit due to those who contributed to project. I owe them one and all.