The material is always zugschluss.mtl
List of file paths for the different types:

Train End Indicator DE (simple)
front:
"vehicle/waggon/zugschluss/zugschluss_de_front.msh"
back:
"vehicle/waggon/zugschluss/zugschluss_de_back.msh"


Train End Indicator DE (double)
front:
"vehicle/waggon/zugschluss/zugschluss2_de_front.msh"
back:
"vehicle/waggon/zugschluss/zugschluss2_de_back.msh"


Train End Indicator AT (simple)
front:
"vehicle/waggon/zugschluss/zugschluss_at_front.msh"
back:
"vehicle/waggon/zugschluss/zugschluss_at_back.msh"


add it to your .mdl file like this for front part

                {
					materials = { "vehicle/waggon/zugschluss.mtl", },
					mesh = "vehicle/waggon/zugschluss/zugschluss2_de_front.msh",
                    name = "zugschluss_de_front",
					transf = { 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, X.XX, Y.YY, Z.ZZ, 1,	},
				},

for back part
                
                {
					materials = { "vehicle/waggon/zugschluss.mtl", },
					mesh = "vehicle/waggon/zugschluss/zugschluss2_de_back.msh",
                    name = "zugschluss_de_back",
					transf = { 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, X.XX, Y.YY, Z.ZZ, 1,	},
				},

where X.XX, Y.YY, Z.ZZ are replaced with the values of according axles where the model will be placed.
Note that simple parts are located at 0, 0, 0 with the bottom of the mesh, the double prims is located 0.859175 / -0.859175 off the middle.

Don't forget to add the mesh id to your RailVehicle configs as
backBackwardParts = { id }, and backForwardParts = { id },

For more information please refer to our forum at https://modwerkstatt.com
