Hole drilling is pretty straightforward. A drilled hole will be ROUND in cross section, very round, Second the hole will be matte finish in the interior, not shiny as it would be if formed hot during the cane making process. Frequently the hole will show circular signs of it's abrasive origin along its length and also as it is difficult to center the hole in the pattern well, the hole will be off center. There are many examples of Italian drilled cane which have shown up across the years. #'s 573 and 578 in Picard's chevron book appear to be drilled to me with the extra clue being that the holes violate the first white pattern layer. I saw not a few drilled Italian specimens during the early 90's when the chevron market here in the US was exploding and drilling large chunks of milli cane and grinding them into beads generated unusual chevron type beads for a market which was obsessed with finding odd and unique chevron beads. Lastly these drilled specimens will show little or no string wear offering a clue to their recent origin. Grinding the bead to look old and distressing the bead with pecks or chips will not effect the condition of the hole surface in the bead's interior.
Modern drilling technique involves a straight rotary drill which leaves a cylindrical hole. Even ultrasonic drills while they don't leave the rotary marks in the hole leave a matte finish due to the abrasives used and the hole will be straight and round. Primitive hole drilling was done from each end and mostly with cone shaped drilling mandrels which leave behind holes with larger openings at the ends than the middle and these holes also are often off center to one another where they meet at the center of the bead. Specimens of this type of drilling abound from Central and South America in pre contact beads, and some post contact beads as well. Virtually all of the older " Tibetan" turquoise beads I've seen and collected from 20 and plus years back are drilled from both ends as are all the old dzi's. All the new world double drilled beads I've seen have much steeper cone shape holes than those from the far east. But then I've only seen several thousands of beads of the many millions out there. There will always show up specimens which run contrary to the general rules. Keep in mind- there will always be someone who will figure out a way or do something differently than others.