[William Cloud Hicklin]

It's nothing more concrete than just a feeling. Like most people's, Tolkien's handwriting changed over time, moving from one variety of awful to another, and the penciled scrawl on the back of the Chronology seems to resemble 1960s scribble more than it does early-50s scribble. But, no, nothing definite can be drawn from handwriting, aside from the fact that notes in ball-point are necessarily from the 50s or later.

My very provisional dating instead has to do with what he was writing when, and the only two texts I can think of that that scrap might have been intended for. (It's perhaps worth noting that, aside from their signatures on the west-gate, Celebrimbor and Narvi appear nowhere in the Lord of the Rings, not even the Appendices.)