Nope, 1-stage 2 speed supercharged Merlin, from the post-war 500 series (very similar to the later Merlin 20 series). Speed, and probably climb, were decreased vs. the G.55. Italian Wikipedia says 609 km/h for the G.59 vs. 620 km/h for the G.55 - no wonder, the DB 605A was making a bit more power in higher altitudes, even restricted.