Board Thread:Questions and Answers/@comment-185.45.70.199-20171011235843/@comment-294304-20171013152056

He has most of those same weapons at his disposal in EXTRA where he explictly isn't a Counter Guardian, but one could argue that he picked them up during the Moon Cell Grail Wars since Servants in the Moon Cell explicitly do remember past summonings; however the odds of him encountering the same figures/weapons to imitate them in entirely different circumstances is...sketchy.

The most likely idea is that he got most of them from either Gilgamesh or his alternate self during the Fuyuki Grail War, if he didn't somehow witness them in his life as a Hero of Justice. Both answers would also explain how he retains knowledge across alternate summonings, as they would have been 'recorded' during his natural history.