Sgian Dubh
David, I forgot to mention that more often than not because I tend to work mostly on a lighter furniture scale, e.g., digging out a relatively small mortice for, let's say, a cabinet rail that's something like 60 mm wide X maybe 18 - 20 thick (with a tenon maybe 8 -9 mm thick X ~40 mm long, plus a square haunch going into a similarly fairly dainty female part, e.g., a leg maybe 40 - 60 mm square, I usually don't even use a mortice chisel morticing. Mortice chisels for small stuff tend to be a bit over-the-top I find, and cumbersome, with a tendency to bruise mortice ends too much, and I tend to choose in preference a plain old firmer chisel, and even a bevel edged chisel to do the job.

Bigger stuff, architectural door mortices, for example were generally attacked with mortice chisels. There was more mortice length and width (~12 mm typically) to play with, plus mortices went deeper, frequently right through material that is around 100- 115 mm wide. Incidentally, I can't recall how many decades ago it was I last hand chopped architectural door mortices, maybe as long ago as the mid 1970s - morticing machines are quicker, ha, ha. Slainte.