that's a nifty looking tool - it reminds me of a sewing tool. I'll track down a video of one in use (and probably get one).
(the brass thing with the buck knife is sort of a novelty - just seeing how far geometry can go - it's not very practical unless someone is truly working on the cheap and few are. Incidentally, HSS in chisels seems to hold its apex much better on metal or wood-metal junctions, but it's *less tough* and not stronger, either. I've never been able to figure out why that is but admittedly haven't tried hard to solve it either - just kept one HSS japanese chisel to trim or scrape infill junctions).