Question on fancy inlays on fretboard

[rockin_ron]

I'm looking at older used guitars and noticing on the elaborate fretboard (specifically the torch and wing) inlay that the detail on some (black line scribing) is either partially or totally gone.  Then on some it is totally intact.  I've attached two examples to illustrate what I'm seeing.  Granted, these are older guitars from the late 90's.  But why the difference.  Is this due to normal playing wear or cleaning/oiling the fretboard wrong?  I thought these inlay details were scribed into the material and then filled with a black filler.  Is this not true?  Any suggestions or known procedures to preserve this artwork detail?  Please don't tell me just don't play the guitar, only look at it.    Thanks!

[B0WIE]

Ink fills are more popular for non contact areas because they can wear from normal use. But, it's not really a bad thing to use them on fingerboards because it's not difficult to touch them up. Finding someone who still does that work may be, but the actual repair isn't hard.

As far as preventing fading goes, you'd need to put a protective layer over the ink fills. Shellac is viable, easy, removable, but will shine the ebony board unless you are precise. I'd probably use a wax. A pure carnauba is fairly resilient. I like Renaissance Wax as it's pretty invisible.

You can also avoid lifting the ink by not oiling the board. Fret boards don't need oil, other than for cosmetic purposes. If the inlays need cleaning, just a damp terry cloth can remove finger grime.

EDIT; By the way, when shopping online, be aware that some guitars will look as the one on the right because they were always that way. If it has wear, you will see traces of the ink fills, especially on the higher frets. The photo on the right looks like it may have never been scribed and filled with the pattern you see on the left.