The terms error and variation (or variety) are confused sometimes. For example, the Imperial Palace 20th Anniversary $5 LE that had a misspelling "EDITON" is a spelling error, but there were 5000 issued, then another 5000 issued with "EDITION" spelled correctly. Since there was no effort to recall the first (misspelled) run, I consider it a distinct chip, but a common one, not an error.

Same thing with the Four Queens Halloween chip -- the error is only because of a Nevada Gaming regulation. All of the chips made their way to the collector market. And at most, Four Queens might have gotten a slap on the wrist by NGC. Describing this chip as an error is a misuse of the term "error" IMO, usually to hype the chip to get a higher price from an unknowlegeable buyer (unless the common nature of the error is in the description).

To be considered an "error", I think a chip should be less than 5% (and in general, less than 1%) of the population of its non-error counterparts. I do consider misplaced inserts to be errors. Same with wrong inlay on one side ($5 / $25 mules for example). Also double-obverse or double-reverse chips where sides are supposed to be different.

I don't consider the H&C version of the Venetian chips to be an error; only scarcer than the more prevelant House mold version of this chip. It does (and should IMO) command a premium price in the collector market, due to supply vs. demand, but it is not an error.

The Caesars Palace $5 house chip with 4-sets of inserts (instead of the common 3-sets) is a closer call, IMO, as to the correct term -- error vs. scarce variation. While it appears that Paulson produced the chip according to a legitimate order from Caesars (therefore, not a manufacturing error), the 4-set insert chips were not consistent with Caesars restricted use of 4-set inserts on higher denom chips only. Since Caesars pulled all the 4-set chips and retrieves / destroys any others found, the chip is definitely a scarce variety, but could (?) be considered an error as well.

The key, IMO, is to decribe WHY the chip is an error or variety, and contrast it to its non-error or regular-variety counterpart, with background facts as to population revealed as known. Then the collector can make their own decision as to its collectibility and value.