Having looked at the pics more closely I am not so sure about this guitar. However I can not make a definitive judgement based on a few photos. Only someone who has examined this personally could do so.
This is a Gibson, made in mid 1980 at the Nashville plant. The truss rod cavity, serial number and general woodworking all look like legitimate Gibson workmanship.
Except for the pickups, this looks like 'the SG' models available at this time.
What is up with the logo though. I can't tell from the pics but it looks odd to say the least.
The routing is very neat, which is a good sign, but I can see no reason for the uneven finish within the cavities. The centre one has no finish at all, suggesting it was added later (also adding weight to this being a converted 'the SG')
I would have a really close up look and see if a central area has been re-routed (or even partially filled and rerouted)
Three minihumbuckers and a (clearly non-original) tailpiece would conceal such a repair quite easily. I can't see for sure. Does the grain match up all the way across the body?
As I say the tailpiece is wrong - the filled stop-tailpiece holes are still evident. It is a genuine Gibson, and so $400 isn't a bad price, but I suspect this has been altered (and possibly refinished) although to what extent is not easily descernable.
You need to have a VERY close look at the body with all three pickups removed.
But despite all this, a really nice looking guitar, that I bet sounds terrific. I would have snapped it up for $400 in a second!