John,
Thank God you build better cues than the photos you take!
I can't tell if it has a swirled design to it like a Bakelite or Marblette?
Is it a uniform dark yellow on the outside, but white if you face it off? If so, I have an old plastic material I got from Abe Rich that was white originally but turns a shade of yellow over time similar to how phenolic darkens over time.
Shoot me an email or give me a call if I can help.
~Beau