In the early 20th century, American Bank Note created a tightly registered printing method of commercial lithography that they called the "Trinity Process." Initially, this was three color (hence Trinity), but I think it expanded to four or more. I don't know whether this was used on stamps that ABNC printed.
Here's an ad that ABNC used to promote the Trinity Process:https://www.atticpaper.com/proddeta...two-sided-ad
Although the company was happy to promote this service to customers, they were protective about how it actually worked. I'd like to learn more about it if any members have more information.