I have to confess I hadn't bought Ivo's book yet (but I remedied that)... I started my book collection with 'leerdam glas', by A. van der Kley-Blekxtoon and another one of hers 'Kristalunie Maastricht' (in Dutch). I figured that regardless of what I eventually was going to settle on to collect, there was a real chance I was going to run into works from these two factories. And it already paid off, since I recognized one Maastricht Verboeket Antiqua vase last week.
I have to say Dutch glass is growing on me. Though the ones I like best (Lebeau really caught my eye) are totally out of reach of my wallet. I innocently remarked to a dealer at an arts and antique fair recently that I liked his purple Lebeau Leerdam bowl best, and he congratulated me on my taste. It turned out it was the most expensive item in his glass inventory at the fair. One of those sold at an auction for several thousands of euros. Oh well. At least Verboeket Antiqua is very affordable

Anyway, sorry for rambling. Those books also have a section on the marks applied by those factories with the known dates.