I think its an old garcia Mitchell?

[Wompus Cat]

Put it back in the car when the Moon is Full and see if it ges stained again . You may be on to something Here.
Seriously ,the chemicals you used in cleaning have  most likely reacted with the Ultra Violet light and Bleached out the Derlin .

[jurelometer]

Kind of shocking that they used Delrin.  A more exotic material back then and required better controls for injection molding.  Bad UV exposure characteristics, so white (degrades fastest) was an awful choice. Mebbe they figured that the UV degraded surface would be less visible on white ... Blech.

If you can get your hands on a copy of Dupont's old Delrin Design Guide,you will find some interesting stuff, like that it doesn't absorb hydrocarbon based oils, and that acetone will penetrate it.  Maybe some stress relief microcracks from the injection molding let some oil in, and the acetone leached it out? Heat from being the car probably helped.

Dyeing white delrin is more common than painting. I think that they even use plain old RIT dye.  It is mentioned in the design guide.  The stuff is paintable, but requires flaming the surface and specific primers and paints.  I never tried painting or dyeing.  On something that old with stress cracks, dyeing may not result in even coloration.

Delrin is one of my favorite materials to work with.  It is a dream to machine as long as you are not looking for a mirror finish or crazy-accurate dimensions...

-J

[JasonGotaProblem]

Maybe ease of machining is why they did it?

Does epoxy stick to it? A light coat with some white tint mixed in (or some other color craziness) seems ideal if it'll stay.

[jurelometer]

Maybe ease of machining is why they did it?

Does epoxy stick to it? A light coat with some white tint mixed in (or some other color craziness) seems ideal if it'll stay.

Probably just differentiating with a new premium material.  Bakelite was not so sexy anymore.

The Garcia sideplates were undoubtedly injection molded.  Too expensive to machine and polish from Delrin stock.  But the gate design for the molds has to be spot on, you can only keep the melted Delrin at injection ready temperature for a short time, etc., etc. 

Bad mold design/processes result in introduced stresses in the part from uneven shrinkage during cooling, which eventually manifest in stress cracks, which apparently is common on these reels.  A wide, disk shape with varying thickness, like a reel sideplate is a tougher part to pull off. A few decades of experience now, so there are lots of molded Delrin mechanical parts like valves out there, but plastic reel sideplates are pretty much all fiber filled nylon for a reason. 

Regarding painting:  Plastics like polyethylene don't have enough surface tension to allow the creation of a a nice even surface film of paint or adhesive for painting or gluing.  Flaming with a torch or similar creates an superficial oxidized layer giving the liquid something to grab onto instead of forming into little pools. Haven't tried this on Delrin, but  assume that the same reasons apply.  I think that they recommend the nastier lacquers for painting Delrin, but I could be misremembering. It should be covered in the design guide.

I personally wouldn't paint or dye an old Delrin sideplate for purposes other than satisfying my curiosity.  Probably pretty long odds in ending up with something that looks better than a somewhat faded or discolored original.  An honest patina ain't so bad.