What brand/model is this skimmer?

[Aquattro]

We'd really need to see close ups of the thing to help figure that out. Check the ETSS line, maybe they have something similar.

[Reef Pilot]

I am planning on taking it apart again, so will get some pics of the internal parts that I am talking about.

But I still don't think it is an ETSS type. I looked at them, and they seemed to be downdraft skimmers, rather than Beckett venturi injectors.

It might well be a DIY, but the main parts must have come from some name brand. Especially this internal cylinder chamber, and the ring, can't see how someone could make those.