Ryan, your bass is a Cort PB-1L, built by Cort in Korea around 1986. Much like the Japanese factories at the time, Cort was building and marketing a whole range of guitars under their own Cort brand (Traditional, Heavy Metal, Standard, Emperador & Acoustic Series)- but they were also an OEM for any number of other distributor brands (who would simply have their logo put on the Cort guitars). That would be the case with your MX-N branded bass.
The PB-1 was part of the Cort Traditional Series. I have one myself in vintage white w/ gold hardware. It's a well made P bass copy- build quality is very good, it sounds decent and has a really beautiful playing neck (the tilt adjustment feature at the heel is a nice Fender feature that you don't see copied often). I don't know that I'd call it rare (but it is from the mid 80's and a lefty, so you won't see them every day). I've seen minty ones go for over $300, and they're certainly worth that- so you did get a good deal.
Hope that helps ya!
... I've always tried to research every bass I've ever bought- and I guess at some point I've bought just about everything once (or twice) .... 
