Digital BW, The Print

I can't imagine how anyone 
> could deal with setting curves for four different colors. That could 
> be a career in itself.

A qaud tone printing job, even as early as 1991 was most likely created by a RIP. Whether it was an off the shelf program or a custom written one, we don't know. The printing 
quality looks fabulous in that book, obviously done by some sort of printing guru. Probably cost more than it was worth.