Monster metropolice

monster_metropolice is the original classname for the Metropolice in Half-Life 2. This entity shows up in the very earliest City 17 maps present in the WC Map pack.

Speculation

Since we have no images of metropolice in-game from this era in development, the behavior and appearance of this entity is up for debate. It is very likely that this entity was used for the earliest Trenchcoat Metropolice design speculated to have been used from 2000 to 2001.

npcweapon_mp5k

Some information that can be gathered from monster_metropolice's usage in maps is that it is sometimes seen using a weapon named "npcweapon_mp5k" (changed to weapon_smg1 in late 2001 maps onwards). This entity does not exist anywhere else in the leak or it's source code. It can be assumed that this was an NPC-exclusive equivalent of the weapon_smg1 entity: Showing an in-between stage after the point of HL1-esque hardcoded weapons in the NPC AI, yet before NPCs were able to use the same weapon entities that players do.

Strangely, npc_combine_s entities from this same time period can be found using weapon_smg1, so there is a likelyhood that this weapon entity is long obsolete by the time of the maps it is found within.

Gordon Criminal Behavior

It can be assumed that monster_metropolice entities were neutral to the player and citizens (acting in a pre-criminal state) by default. This is because of an env_global entity with a "gordon_criminal" value being set whenever hostile metropolice are supposed to be present in 2001-era maps.

This is reversed in the 2003 leak and final game, causing npc_metropolice to behave hostile by default and requiring an env_global to become passive.

Hand-to-Hand Combat

It can be assumed that this entity once was able to engage in the hand-to-hand combat system described as being used within Get Your Free TVs, causing a metropolice and citizen to brawl in a funny-looking fisticuffs fight.

The police might have been using nightsticks for this system as Marc Laidlaw once described a cop during GYFTVs as trying to "konk the citizen with his nightstick". There is further evidence to support this such as textures being present for a nightstick (the "W_stun" textures found in the police materials folder) and the leak citizen code referencing a cut animation activity named "ACT_HH_CLUBHEAD_BLOCK".

Mitigation / Entity Migration

In most cases, simply changing the classname of a monster_metropolice to npc_metropolice will work fine without any additional changes required.