Be sure to descale and take a straight edge to it. I see the very end of where the threads were.

if looks straight might be threaded to French, BUT hand held dies are not really to be used to cut threads from scratch.
possibly a VAR tool as the examples I have seen are adjustable in circumference.

If successful, you would need two French threaded parts, top race and nut.

i really doubt a machinist would turn it down to 25x 1 threading. Think about how it would be held and the swing and imbalance of theblades.