Yup, that is true. Fender used nitro on the headstock faces after they switched to poly for the rest of the neck because the logo decals reacted badly when top-coated with the poly finish. Supposedly they used nitro on the headstock face until around 1980, but I can't solidly confirm that. Here's an article that mentions the nitro faced headstocks (and says some not so good things about the thick poly body finishes of the mid 70s):
"The mid 1970s also saw the adoption of the so-called 'thick-skin' finish, which consisted of as much as a dozen polyester undercoats that stifled body resonance and imparted a harder, more plastic look (sprayed body color coats and topcoats were still nitro lacquer). As quoted in author Tom Wheeler’s The Stratocaster Chronicles, Custom Shop master builder Mark Kendrick noted, “They just blew a tsunami of polyester on there,” and “Encapsulating the guitar in a cocoon of plastic like that is going to dampen the sound.” As described by Richard Smith in Fender: The Sound Heard ‘Round the World, these heavy finishes were “durable but unmusical, almost sticky.” Concurrently, many headstocks faces were seen to age differently than the necks they were part of, because while necks were finished in polyester, which resists aging well, the headstock faces were finished in lacquer, which ages noticeably, over the decal, because polyester and the decals reacted adversely."
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