K=strikeout. Any update from RHDAS?

[Sam Clements]

RHDAS says that "K"to mean "strikeout" in baseball scoring originated with :
l.  New York Herald sportswriter M.J.Kelly, in the 1860's.
2.  Henry Chadwick, 1861.

The attributions for the assertions are T. Considine, 1982 for the first,
and Dickson, 1989 for the latter.

Lighter says "neither source offers documentation."

So, any documentation?