From Quake Wiki
This entity spawns the Red Armor.
Model: progs/armor1.mdl (skin 2)
If the player is wearing better armor they will not pick up worse armor unless it is heavily damaged - how much depends on the armour type being worn, how damaged it is and the armour type being picked up.
targetname - Can be killtargeted
target - Will trigger this entity when collected
Like the other armour items, ArmorInv is 32 units wide/deep and 72 units tall. The bounding box, from the origin is as follows; '-16 -16 0', '16 16 56'. If any of these extents clip through level geometry then the item will fall out of play on map load.
If armor starts a level sat on a func_wall which is later killtargeted then the armor will not fall, but instead hang in the air as if the func_wall was still there. If you do want armor to fall off of something then use a func_door that moves horizontally next to some other geometry to 'scrape' the armor off - it will fall once there is no solid brush below it.