For more background information about the T-51b and its appearances in other games, see T-51b power armor. For an overview of various models of power armor in the Fallout series of games, see Power armor.
“The T-51b powered infantry armor is designed with the latest passive defense features for both civilian and military disturbances. The back-mounted TX-28 MicroFusion Pack generates 60,000 Watts to power the HiFlo hydraulic systems built into the frame of the suit.”— Power armor specs
T-51b powered Infantry armor or power armor represented the peak of armored infantry technology before the Great War. Now, only the most technologically advanced factions with ties to the pre-War American military or federal government, such as the Brotherhood of Steel or the Enclave, have access to this type of power armor.
Note: After the first lockpick attempt all nearby Brotherhood members turn hostile. Senior paladins and senior scribes do not come out of the storeroom, so the second attempt is impossible (when closing in on the door, the battle starts).
The initiate is in the Old Town section of the Hub. He will be located in the building directly below the entry point. He can be freed by killing his guards.