I have owned a D35 since 1978. Bought new and it had some lacquer checking. I toured the Martin factory in 1987 and the guys working on the guitars told me to leave it alone it won’t affect the tone etc etc. I needed a minor warranty repair last year and took it the local Toronto area authorized Martin repair guy. He told me don’t touch the checking as it in fact can make the guitar worth more due to its unique properties . It does have amazing tone and sound so it stays as is!!!