Garlicdude said:
"My educated guess would be 4140".

I'm inclined to go along with you, Karl, especially if its tempered to
around Rc 50 or so.

A tool & die shop I had as a client made envelope dies from 4140 and
tempered as I stated. I was taken aback at this use of this steel,
but, the cutting edge lasted long enough for their customers to be
happy.

BTW: Envelope and label dies are used to stamp/cut labels and small
envelopes from a thick stack of paper. The paper is placed on a wooden
board into a press, the die in the shape of a cookie-cutter is placed
on top of the paper stack, and the press operated. Voila, a stack of
envelopes or labels result. Crude but effective. For large labels or
envelopes the die is bent-up from 1/2" x 3" proprietary steel bars,
heated and welded into a closed form. Think of steel rule dies, only
MUCH more substantial.

I think this steel would work well in the tree-trimming business. Best
of all: it is cheap and the heat treatment is a cinch. The heating
ought to be done in a furnace, though, to ensure uniform properties
throughout.

Trust this helps.

Wolfgang