Hey nonie, this is a signet ring of his family crest. All men in his family wear this ring which was given to them by his father, Colin. Once Henry gets married it will go to the other hand, ????

It shows a knight riding a horse.  

BTW fun trivia, and also another proof that Henry doesn’t just give his movie roles a lot of character and background but also a major geeky geek: in The Man from Uncle Napoleon Solo wears a signet ring just like Henry. 

According to the movie’s costume designer, having Solo wear that ring was Henry’s idea. The signet ring has the emblem of the two-faced god Janus, which among many things (new beginnings, pathways) represents duality and to my assumption tells us of Napoleon’s cunning and fickle ways.  

Now I hardly believe it was given to him by his father. Solo’s dad was a Janitor but then the word “Janitor” actually comes from the Latin word Janus which means doorways, gates etc (MIND BLOWN). So It’s kind of Henry’s way of showing that Napoleon makes his own way. Okay, enough geek for today!!!