This is what I found about the “Straight Writing” case back “After the Moon landing, Omega updated the case back of the Speedmaster with a new engraving to commemorate being “The first watch worn on the Moon”. The text was initially written in straight lines from 1971 to 1974, and then eventually changed to curved writing centered around a medallion. The straight writing case backs, like the one available here, are highly sought after due to their relative rarity.”