What does Grenade Launchers do in AoE3?

Ships 1 Spanish Treasure Chest; Gives: DE Grenadier Enable; Grenadier: line of sight +2; Makes researchable: Incendiary Grenades. The game says: "Enables Grenadiers to be trained and equips them with a hand mortar, which quickly propels explosives and increases their range, +3 Uhlans."

Home City card

Grenade Launchers

Grenade Launchers (tech ID DEHCHandMortarGerman) is a Home City card in AoE3: Definitive Edition 100.19.18309, in the decks of 1 civilization, sent from the Fortress Age. Effect: Ships 1 Spanish Treasure Chest; Gives: DE Grenadier Enable; Grenadier: line of sight +2; Makes researchable: Incendiary Grenades. It hands over about 450 resources' worth.

Quick answers (3)

Which civilizations have the Grenade Launchers card?: Germans.
What does Grenade Launchers do in AoE3?: Ships 1 Spanish Treasure Chest; Gives: DE Grenadier Enable; Grenadier: line of sight +2; Makes researchable: Incendiary Grenades. The game says: "Enables Grenadiers to be trained and equips them with a hand mortar, which quickly propels explosives and increases their range, +3 Uhlans."
What is the tech ID of Grenade Launchers?: DEHCHandMortarGerman.

Enables Grenadiers to be trained and equips them with a hand mortar, which quickly propels explosives and increases their range, +3 Uhlans.

What it does

Ships 1 Spanish Treasure Chest(unit)
Gives: DE Grenadier Enable
Grenadier: line of sight +2
Makes researchable: Incendiary Grenades
Ships 3 Uhlan(unit)

10 further effects (interface, visuals or AI) not listed.

What it hands over

3 × Uhlan150 each

Total ≈ 450 resources — units at their train cost, crates and animals at what they hold.

Cost: 1
Sent from: III
Times it can be sent: 1
Game ID: DEHCHandMortarGerman

In these decks

GermansIII×1

Source: techtreey.xml and the Home City files, AoE3: DE 100.19.18309 (build 25040513).