I wanted to jumpstart this topic and show an example of the earliest Camillus tang stamp that I have seen. This is the one that has the curved CAMILLUS/– . –/CUTLERY Co./NEW – YORK on both blades.
According to John Goins’ book;
Goins’ Encyclopedia of Cutlery Markings, this is the earliest tang stamp Camillus used. Goins dates this tang stamp as 1902 – 1915. Notice the tang stamp is identical on both blades, including the font style which is sans serif.
This is the first example I have seen, (and added to my collection),

of this earliest tang stamp.
There are other tang stamps used in 1915 & 1916, (per Goins) that use the curved top line CAMILLUS with the – . – beneath it but they were used in conjunction with a different three line stamp on the other blades. You can see these illustrated below on a copy of Camillus tang stamps from Goins book.
If Goins is to be believed Camillus actually could’ve used as many as five different tang stamps in 1915 in 1916. Why would they do this? I have no idea though part of the answer may lie in knife production for World War I. I know Camillus made knives for the Canadian Navy during World War I and a lot of knives for the US government. Those may have in some way been the driving force behind the plethora of tang stamps used around the time of World War I.
This little half congress obviously has some problems, the pivot pin for the master blade is worn out, and I think that is contributed to the cracking of the bone. Someday when I get really bold and have a lot of time I may try to repair this, but in the meantime I’m going to leave it as it is and add it to my collection as the only example I currently have of the first Camillus tang stamp.