Looks like a metallic color with a high value for F0 in the .mtl, something like 1.0. And the tail has probably a value of 0.1 or lower.
Both parts have the same values
:
"mats" : [
{
"name" : "bt67_1_T",
"color" : "1.0,1.0,1.0,1.0",
"f0" : "1.0",
"roughness" : ".5",
"no_light" : false,
"alpha_masked" : false,
"tex_albedo" : "./texture.CargoNorth/bt67_1_T.dds",
"tex_normal" : "./texture.base/bt67_1_T_BUMP.dds",
"tex_roughness" : "./texture.base/bt67_1_T_spec.dds",
"tex_opacity" : "",
"tex_reflectance" : "",
"tex_environment" : ""
},
{
"name" : "bt67_2_T",
"color" : "1.0,1.0,1.0,1.0",
"f0" : "1.0",
"roughness" : ".5",
"no_light" : false,
"alpha_masked" : false,
"tex_albedo" : "./texture.CargoNorth/bt67_2_T.dds",
"tex_normal" : "./texture.base/bt67_2_T_BUMP.dds",
"tex_roughness" : "./texture.base/bt67_2_T_spec.dds",
"tex_opacity" : "",
"tex_reflectance" : "",
"tex_environment" : ""