Uncanny X-Men Vol 1 151 page 11 Sentinel Mk IV (Earth-616)

The creation of the fourth model of the infamous Sentinels was authorized by the US Government following the attempted assassination of Senator Robert Kelly by the Brotherhood of Mutants. The government contacted industrial tycoon Sebastian Shaw - unaware that Shaw was a mutant himself - and requested his company construct a new breed of Sentinels as part of Project: Wideawake, an illegal government plan to conduct research on superhumans and mutants and - if necessary - capture mutants who posed a potential threat to national security. Shaw had other plans for his Sentinels, however, and used them to attack the X-Men without notifying the project leaders.

The Mark IV Sentinels possessed all of the attributes of the previous models, as well as searchlights built into their chests and a learning program that would provide Project: Wideawake with vital combat data on mutants, allowing them to design special weaponry to deal with specific mutant threats.