I know a fair bit about Napoleon and Josephine, but I did not realize that he gave her an engagement ring, or that it was this contemporary looking.
Napoleon commission a two stone ring, with a diamond and a sapphire in the toi et moi style (two stones set beside of adjacent to each other). They are each just under a carat in weight.
Engagement rings had been common among the aristocracy (likely because they would have been very expensive to make), and didn’t become truly popular until the 1900s for everyday folk. Diamonds were not commonly used until DeBeers’s 1947 campaign. So Napoleon was ahead of his time in more ways than one.
This was auctioned in 2013 for about $950,000.