From my understanding, it's either an fmp parts kit assembled by special weapons using all Fmp parts, or its got some us made parts, either way they look to be a good value if its indeed all fmp parts.

I have one in my collection.  They are very nice.

I had one, and I'd say it's as good as it gets.

I have one and also one that is an FMP imported back in the 80's and they look and feel virtually the same and the quality is the same.

Varies widely.
The receivers were marked only with the importer ("Interport"), city (Delta, UT), and a serial number, and imported as such.
They were imported and sold as stripped receivers, so just because it says Interport Delta on the side, doesn't mean it had any particular type of parts.
I've been watching these whenever they've come up for sale on Gunbroker or whever for the last several years, and they've had everything from HK, FMP to POF and unmarked parts in them.  No way to know without inspecting it.
GENERALLY, since these were imported about the time the FMP parts and kits were in massive supply, that is common in them.