Hello Paul, welcome to the forum. I’ll see how much I can help you out here but if some of the info is already well-known to you, just 🙄 and scroll down until something (hopefully) worth reading appears.

BC Rich guitars are either made in the US or the NJ series made, as you know, in South Korea. Both offer good value as 2nd hand buys because the uber-metal looks are not to everyone’s taste. Koreans, in my experience, deserved credit for their builds long before the recent upsurge in prices for their Squiers, Fenix etc. The biggest downside is that some hardware is on the cheap side and the most annoying offender is usually the jack socket. If your son gets that PFZZ-DURR-DURR noise when moving around then the socket’s the likely cause and a few $ on a Switchcraft socket and an easy soldering job completely cured my Fenix.

So, NJ series just means it’s made in Korea rather than US. The “Virgo” is the model and determines its shape and spec. I did manage to find a NJ Virgo Celtic that sold low for $132, probably because of cosmetic damage:

http://www.bass-guitar-museum.com/bass-16468-BC-RICH-CELTIC-VIRGO-BASS-GUITAR-ONYX
http://www.bass-guitar-museum.com/vignette/bass/23/380101965375-2.jpg

The only difference to yours should be “Celtic” which is the fancy fret markings. Some nice features. 2 pickups, I know it looks like 4 but the pickups are “split coils”, so a coil handles the E and A strings with the other coils covering the D and G. The arrangement reduces mains hum. The four knobs are either two volumes (or a master vol and pickup blend – easy to tell) and, because it’s active, there’s a treble boost/cut and bass ditto. A 9V battery inside that back panel will need replacing if you get severe distortion or no output at all. That little plastic bit where it says “Virgo” is the truss rod cover. Adjusting the truss rod straightens the neck but don’t try that unless you know how. Those pickups are easily upgraded (anything that fits a Fender Precision) but Korean pickups are quite reasonable.