Since you may not be dealing with new items all the time I would like to discuss how to spot a Slash by looking at the box. The best way to do this is too look at the label in the lower left hand corner. Below is a picture of some AUTHENTIC Sierra release labels:
And now for a Slash release:
So lets talk about these. First the Sierra labels are always stickers, while the Slash labels are just printed on the cardboard. Slash labels are almost always black lettering on a white background, while Sierra labels usually are blue or gray or both! Occassionally, with the SCI1 releases (thicker box), the Slash releases won't even have a specifications label so you will want to look carefully when purchasing these games. Note that, sometimes with this style of box Sierra put the labels on the side of the slip case, so if you don't see a sticker on the front be sure to check the side before labeling it a Slash.
One other thing to look for is a "Value Priced" sticker:
These are also Slash releases (notice the Minneapolis area code for support) but they are a little better quality.