Check it out against the Luna Pro in various lighting conditions. I'd use incident readings instead of reflective, or a grey card so that there are no variables in what the meters "see". If they match closely enough to satisfy you, there isn't much reason to not trust it.
If you're doing once in a lifetime pics though, you may want to use the meters in parallel for bit. Or else save working with the Scout for a time you aren't doing critical shots. However, if you pay attention to what it's telling you, you can generally figure out whether or not it's giving you a reasonable reading.
I have a selenium Scout, it's been reliable and accurate within its range.
Meters that are two stops off aren't meters, they are decoration.