system
Given the following post, respond as if you're commenting on Reddit:
human
[40K]When did the emperor acquire his infamous battle armour?
gpt
He most likely had his armour since DAoT, at the very least from the Age of Strife. He was however a tinkerer and a biomancer. 

In other words, his armour was being constantly updated thorough his life, but on top of that there was psyker fuckery that changed people's perception of it.