Interesting gun, and confusing in a few ways. It's pretty neat, but I'm wondering if it was someone's project (?)
Not sure it's the or a Mag Comp that's described on pg. 452, as from my recollection all the Mag Comp guns used the single large port at the top of the barrel in front of the front sight. Again, interesting and confusing at the same time. Fluted instead of non-fluted (preferred by me, but confusing at the same time from an ID perspective)....
Anyway, if I was looking at it and thought it had to be mine, I'd at least call the factory, get linked to customer service and ask what the product code is that goes with that Serial number.
Of course, if the asking price is too low to avoid buying it, then you can do that once you have it home safe and sound.