1960s Pilot Black Resin/plastic?

I have a few Super and E series Pilots with the "fingernail" type nibs that have cracks in the section, rendering the nibs loose and the sections leaky... I had one that was bad enough off (and I needed the cap and barrel for two other pens), that I broke it apart to learn about the feed retention method and the material. This "experiment" made me think that at least the section on these Pilots might be acrylic, as it was quite rigid and resilient, as well as breaking cleanly once it finally gave. Does anyone know for sure what the plastic is and/or what cement or solvent might work to stabilize the other cracked sections I have which are holding a couple of otherwise great pens back from re-entering service?



It looks like SCI 16 or 4 might be useful, but I've never used either before.



Thanks!