There's some individual interpretation involved in the dividing line between errors and varieties. Here's a few examples:

These 3 Mapes $1 yellow chips were made by TR King (small crown mold) to have 4 different color inserts - 1 each of black / red / green / blue, but not in any particular order. You will find all 3 varieties out there. Usually referred to as "Black opposite xxx" where xxx = one of the other 3 colors. Not an error, as quantities of each were used, and were not a quality control error.

This Luxor $1 chip, made by Chipco, comes in 7 different varieties. One without any UV marking, and the other 6 with different markings, as seen under UV light. See the Luxor page on the ChipGuide for pics of the UV markings. Again, these are varieties of the $1 Luxor series, as the different markings were intentional.

These 2 Caesars Palace $5 chips are different, with the chip with 4 sets of inserts being an error. The 3 sets of inserts is the correct rack chip for its time. However, a substantial order of the 4-sets was ordered, delivered and some put on the tables. About 100 of the errors got out, but the rest were destroyed, as discovered. So ... an error, even though there are 100 of them.

The Venetian poker room has an interesting series of regular / 1-error / and double-error chips, that I'll explain another time.

Most errors though are 1 of a kind or very small quantities. I think of an error as something wrong that occurred in manufacturing that, if Quality Control observed it, it wouldn't have left the factory. There are still other types of errors, but that's a start.

All pics from MOGH / ChipGuide

BTW, I would consider your Nevada Club chip as an error.