All the main body shell was urethane resin,
most of the bigger exterior parts too.
The smaller details like the rear turret tracks,
'U' shaped handles, top light guard
and various other bits were pewter.

Head and tail light guards were just steel rod.
Reference for this little turnout was the
Colonial Marines Technical Manual,
the Halcyon APC kit and a stack of stills from the movie.

Granted it's not completely accurate but the best I could do
and some compromises had to be struck,
mainly due to the interior detail.