So other than a Transposer, I guess this will be really useful for calibrating VCOs.
So guessing I'd need a really accrurate Multimeter to calibrate / check this?

Enjoy your spare HP, don't rush to fill every last space, this is not like filling sticker books. Resist the urge to 'complete' your rack, its never complete so just relax.

https://youtube.com/@wishbonebrewery