Warren in Lancaster, PA
I had one of these long grind mortise chisels too. I bought one from Lee Richmond. It had not been used for mortising in years; the side edges were way too worn and rounded for it to be used effectively. However Lee had freshly ground a long bevel on it and honed a very small "secondary bevel" to conform to what he was seeing on the internet. Once I straightened out the sides it was usable, but was much better when I made a full flat bevel on it.

This reminds me of a 2011 double iron discussion:

I do not see a lot of evidence in older planes that they were universally used in a way that would improve surfaces, especially in old woodies