I found a video of it. You can find it around 1:20 or 1:21. Yes, it's the purple gun.
http://www.youtube.com/watch?v=bQ5WvsdmuUw
That's from Master_Unreal's remake project. That isn't the original mesh at all, but he used the skin found in the 98 beta(because it still had the impalerbolt among the classes) and applied it on the unknown weapon/thingy from the mesh utility tools, that model being early 96 but I don't think that was the impaler tbh, it had no anims also and he added the impalerbolt crystl to the mesh as well. But that's not the original gun/model.
The original gun/model had this import code and this is from late 1996(except the mesh we don't have/mesh sources for the version):
MESH SEQUENCE MESH=Impaler SEQ=All STARTFRAME=0 NUMFRAMES=1
MESH SEQUENCE MESH=Impaler SEQ=IMPLR001 STARTFRAME=0 NUMFRAMES=1
MESH SEQUENCE MESH=Impaler SEQ=SLASH001 STARTFRAME=2 NUMFRAMES=20
TEXTURE IMPORT NAME=Impaler1 FILE=\Unreal\Models\Impaler1.PCX FAMILY=Skins
TEXTURE IMPORT NAME=Impaler2 FILE=\Unreal\Models\Impaler2.PCX FAMILY=Skins Palette=Impaler1
MESHMAP NEW MESHMAP=Impaler MESH=Impaler ; Assign name and mesh to new sprite
MESHMAP SCALE MESHMAP=Impaler X=0.1 Y=0.1 Z=0.2
MESHMAP SETTEXTURE MESHMAP=Impaler NUM=0 TEXTURE=Impaler1 ; Apply textures
MESHMAP SETTEXTURE MESHMAP=Impaler NUM=4 TEXTURE=Impaler2
Basically, if you are lost what this means is that this was a completely different mesh/skin and had two slots of skins and actually had melee anim/function. That is because all the weapons had melee functions back in 1996 if ran out of ammo or in case of some like automag or impaler just melee closeup attack aside from fire/altfire.