I wonder what they'd do if I walked up and filed the corners ("just checking!").
that aside, I typically use cans or a pair of exhaust pipes with a layer between (the latter for longer chisels) to do heat treat and not use a typical forge like you see on TV (have one, but temp and heat control isn't as good as something more specifically designed).
I could maybe heat treat something like that with a dip tank and a forge made out of a small boat funnel!
they are not as good as a marples carver handle, but they look a lot better. probably the number one request that I get is "can you make me a big set of paring chisels with london pattern handles?"
that's a clue that someone wants chisels to collect and not to use. there are plenty of people who will make chisels for profit that will finish them nicely and maybe add purchased london pattern handles, but I haven't ever had a professional woodworker ask for them.
And I wanted to like them since they look the best - if you're going to try to make chisels that are top users at first, you hope that they'll be able to have the jewelry look, too, but they just aren't capable of disappearing in your hand in use like a simple carver's handle.