Amazingly, there isn't any real clear direction on these bayonets. The cut quillion design, either modified or made that way did occur sometime between 1915 and 1918 depending on the source. Also depending on the source, it was only for cavalry units, not all units. i have several of these bayonets, not sure what type the others are, I'll have to dig them out when I get a chance. One of them is the black bakelite, I do remember that.
According to my sources, the hook was modified between 1918 and 1925.
BTW the reinforced socket dates from after 1912 and the composite handle from before 1917.
Let's not forget that there are always exceptions that confirm the rule, especially in French military history.
I checked McCollums book. He says the shortened hook began in September of 1918. He's researched it pretty extensively for his new book so that is most likely correct.