I was reorganizing my circlip pliers and found I had three made in the U.S. by Waldes-Truarc:
The one at the bottom is very clever, since, by changing the pivot position, it can be switched for use with both outside and inside snap-rings.
I can't find out much about the company, aside from the fact that it's been in existence for almost 75 years, and it introduced 2 types of retaining rings for aircraft use in 1942. It was acquired by SKF in 1985.
The German Seeger-Orbis website states that one of their employees, Hugo Heiermann, first patented the retaining ring as a "Bolt Locking Device" in 1927, and claims that these are still colloquially referred to as "Seeger rings" in Europe.