The, "Presented" trophy is actually a nickel/silver mix. Since it goes through so much rigorous handling, to have it all silver would be a bad idea. It'd be more bent and lopsided than a ball of silly putty sitting in the sun. Also in the vault at the hall, the original Neck/smaller columns which the bowl sits on have been retired. It was this neck which assisted in the transformation from the cigar or "Smoke stack" look the cup once had, to the more familiar look which it has today (5 band barrel with 3 ring neck + bowl)
There used to be mistakes/flaws on the replica cup (circa 1993) but they decided to redo the bands which had these mistakes on them around that time so yeah, no flaws or mistakes are on the replica.
You're right Sky, each band can hold 13 years worth of names/teams on it but in 1965 when the Habs won it they actually used two spots on the cup to list the names of its winners. So there are only 12 teams listed on that band as opposed to 13. This ultimately threw off the scheduled time in which the cup was to be filled. Ironically enough, it was on schedule to be filled during the 100 Year celebration of the cup at the completion of the 1993 season, marking a turning point to add another band to the bottom.
There is more info to be reviewed at
http://en.wikipedia.org/wiki/Stanley_CupAnother tidbit of info, there are actually 2 names scratched on the inside of the barrel. Phil Bourque, when he won it in '92 with the Pens (I believe it was that year, might have been in ’91 when he did this..) had the cup delivered to him and it fell apart in his living room. He ran to his shop to get tools to put it back together and in the process, discovered a name on the inside of the barrel. Before he put it back together, he decided that should they ever change the format of the engraving of the cup; his name will forever be etched inside so he scratched his name and the date inside. So the names on the bands may become retired, but his will forever remain on the inside

Another note, the Stanley Cup and the Grey Cup (CFL) are the only trophies in professional sports to sport the names of the teams/players in which win them. They’re also the only professional sports trophies to be awarded annually, unlike the NBA, NFL and MLB where a new one is made and awarded every year.