This lovely object is more than just an interesting gewgaw: It’s called a “turner’s cube”—so named, I think, because it is a challenge for one who turns on a lathe rather than eponymously—and according to Bob Warfield, “[i]n the old days, novice machinist’s [sic] were handed one and told to work out how to make one of their own.” Bob’s got a cool page describing his efforts to make one manually and then using a CNC mill, with some bonus commentary on this thread by CNC Zone member widgitmaster, who made the cube pictured above, using the jig pictured above, on a big engine lathe. Beautiful!