Hello,

by chance i just finished restauring an old sheffield that was broken at the same location. I soldered it with a spezial silver solder paste. Two aspects are important when doing this. You must use a very hot and focused flame (best is a propan or butan burner combined with oxygen) so u can bring in much energie in short Time. The second thing is, you must cover the rest of the Blade with wet tissues and sprink Water on them all the time. So a helping hand is recomended.
I managed to get it very close soldered and the brand is still visible. A little solder line will always remain, but i think thats better then nothing...

By the way, drilling hardened steel is no problem if u use a carbide drill. So the other solution of making a kamisori style razor out of it works too.

Good luck, and dont give up on it.

cheers,
Ulrik