wouldn't surprise me if the spindle was as hard as the punch
The ones I've seen are not, at least on the ends as pictured. There IS always the magic marker indication with a careful resolve to not erase them.
You could also take the procedure a step further using a Dremel with a stone grinding tool, should hardness prevail. Just a touch-off mark is all that's needed to ID.
Carbide or diamond tipped (vibrating) engraving tools or simply a hand held Machinist scribe with the same type tips, will suffice too!
AND...nail polish works!
Lots of options.
