Very neat Dave!
Back in 2017 I had a dabble with that circuit, simply out of interest, obtained all the bits from here and there and knocked up a PCB, but it was overtaken by other projects. Given that I have several functional signal generators, it made little sense to build it, other than the fact that I enjoy taking circuit designs (invariably other people's!) and turning them into finished projects.
https://www.vintage-radio.net/forum/...d.php?t=140451