There is no functional difference between the regular combat knife and the trench knife, only the visual touch of a spiked knuckle guard. It can be repaired using standard combat knives.
Stabhappy - Stabhappy shares all of its stats with Occam's Razor, but has two principal differences. Firstly, the raider that holds it respawns, allowing multiple copies to be obtained. Secondly, it deals an additional 50% damage to limbs.
Sim version combat knifeOperation: Anchorage (add-on) - A sim-only version of the weapon which differs only in health (essentially non-degrading).
Although used during the Anchorage Reclamation simulation, you can obtain it for use in the Capital Wasteland by retrieving it from the sealed armory in the Outcast Outpost after completing Operation: Anchorage.
The following is based on Fallout 3 cut content and has not been confirmed by canon sources.
Schematics for the trench knife are included in Operation: Anchorage's game files, but were not placed for the final release of the add-on. The schematic called for one combat knife, one brass knuckles, and one wonderglue. The schematic is completely unimplemented, in that the workbench script has not been updated to allow the item to be crafted, even if the player possesses the schematics.
End of information based on Fallout 3 cut content.
In the Spanish version of Fallout 3 the trench knife will appear as "combat knife", making the game confuse it with the actual combat knife, thus making the trench knife a regular combat knife.
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