The katana that Lucas picks up is one of the various unlicensed "replicas" of Duncan McLeods dragon head katana from highlander the series
As established earlier in the season, Lucas is supposed to be roughly the same age as Clark, and therefore six years younger than Lex. In real life, Paul Wesley is five years younger than Tom Welling and ten years younger than Michael Rosenbaum.
Since Clark's rose is still in the rubbish bin without any signs of wilting, this episode probably takes place the day after the events of Rush.
The Season 2 DVD contains a deleted scene in which Lex gives Lucas a tour of the mansion before taking him to meet Lionel. Lucas correctly guesses that the mansion came from Scotland. Lucas comments that it's a strange family that makes you sign paperwork before you can join. Lex tells Lucas that his mother is in the Metropolis Sanitarium.
Lucas Luthor is the child that Rachel Dunleavy gave up for adoption and mistook Clark for in Lineage.