what plastic? 2003 silverado sportside rear fender

[mr.fixit]

I have a 2003 Silverado with the sportside body. To repair a crack in the rear fender, I need to know the type of plastic it's made of. I have not found a clearly readable 'plastic identifier' stamped into the part. Because I can do the repair without removing the panel from the bed, I can't inspect the entire piece. But, along the bottom edge is an almost unreadable stamping that reads:

 

P/N (unreadable)

MADE IN CANADA BY

POLY(SIM?) (unreadable)

(unreadable)

 

From the inside, the plastic is a yellow. Anyone know what these are made of? Or does anyone know where on the part a more readable identifier is stamped?

 

I hope this is the right forum. If not, which should I try. Many thanks.