What does Extensive Fortifications do in AoE3?

Castle: build limit +100%; Frontier Fortification: hit points +25%; Walls: hit points +25%; Agra Fort: hit points +25%. The game says: "Enables you to construct twice as many Castles and increases the hitpoints of ALL fortifications!"

Home City card

Extensive Fortifications

Extensive Fortifications (tech ID YPHCExtensiveFortificationsIndians) is a Home City card in AoE3: Definitive Edition 100.19.18309, in the decks of 1 civilization, sent from the Colonial Age. Effect: Castle: build limit +100%; Frontier Fortification: hit points +25%; Walls: hit points +25%; Agra Fort: hit points +25%. It hands over about 100 resources' worth.

Quick answers (3)

Which civilizations have the Extensive Fortifications card?: Indians.
What does Extensive Fortifications do in AoE3?: Castle: build limit +100%; Frontier Fortification: hit points +25%; Walls: hit points +25%; Agra Fort: hit points +25%. The game says: "Enables you to construct twice as many Castles and increases the hitpoints of ALL fortifications!"
What is the tech ID of Extensive Fortifications?: YPHCExtensiveFortificationsIndians.

Enables you to construct twice as many Castles and increases the hitpoints of ALL fortifications!

What it does

Castle: build limit +100%
Frontier Fortification: hit points +25%
Walls: hit points +25%
Agra Fort: hit points +25%
Ships 1 Hindu Villager(unit)
Ships 2 Sepoy(unit)

What it hands over

1 × Hindu Villager100 each

Total ≈ 100 resources — units at their train cost, crates and animals at what they hold.

Cost: 1
Sent from: II
Times it can be sent: 1
Game ID: YPHCExtensiveFortificationsIndians

In these decks

IndiansII×1

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