Really excited by this collection; been waiting for something like this for my entire life, as my passion is historic instruments. Used to visit Von Heune's workshop when I lived in Boston MA.
Now I just have to figure out how to buy both volumes and whether/how to pre-buy vouchers to pay for it. Looks like you can buy three $100 or 100 euro vouchers and get the fourth for free, thus funding the full purchase.
Except I haven't figured out yet whether both volumes are already available and/or whether the price is for both.
Argh; I am working 12-14 hours a day for a long time now, so "slow" purchases (that is, ones requiring lots of analysis of clauses, fine print, hidden paragraphs, looking at multiple information sources, etc.) cause me to delay purchases until a weekend or holiday.