Case bone - delrin mismatch?

[Nature Boy]

I'm curious on any thoughts about this Case 6233 I picked up a while back. I guess I never really examined it until today.
It seems like the mark side is bone, and the pile side appears to be delrin.
Was this a thing? QC error? A previous owner's mod?
Appreciate your time and any thoughts!

 

[jc57]

Looks like someone replaced the pile-side scale at some point in the knife's history.

 

[Nature Boy]

That's what I was figuring.
Guess my thought to go along with that was, "was more of this knife made of replacements?" It's not a big deal to me, as I didn't invest much, and didn't intend for it to be an investment.
Wondering if anything else looks noticeably out of place.