The first thing I did was to redraw the shape of the blade. I did a total regrind of the blade and after going through the stones up to a full uchigumori finish, i gave it a mirror finish. Then I built a new handle and a new saya for it (still in the making). The seller stated that the steel was true tamahagane, but that is not very likely. It is probably a blue steel variety. That said, the edge is even harder than my shiroko honyaki @HRC 65, and takes an absolutely incredibly sharp edge. This is very possibly my sharpest blade to date. Even sharper than my Doi Shiro #1. Some pictures from the process below. Enjoy.
Before: Note the odd "hanging" profile of the knife including the handle. It almost looks a little bit depressed :o)
After: The profile is "straightened out" to a more balanced appearance
After: Polished machi :o)
In the below picture you can see the reflection of my ceramic wall tiles in the blade. Note the semi polished blade road. Towards the very edge you can see the reflection lines from the tiles "bend" a bit due to the hamaguriba (clam shell) sharpening. The reflection amplifies the hamaguriba curve significantly because the blade is held askew related to the tiles, but it shows the principle of hamaguriba.
Before: Simple handle... not at all bad, tho'. Ho wood and water buffalo bolster.
After: Custom (by me) Macassar Ebony octagonal handle with silver inlays and water buffalo bolster :o)