I recently bought a 2009 Abarth 500 esseesse, I found that it does not have the original downpipe catalytic converter, but with a de-cat pipe instead.
But there is another catalytic converter further back after the flexi connection.
And the O2 sensor is moved down after the cat. It looks just like original.
No engine fault code.

May I seek you guys help in solving my puzzles?
1. Is it a commercially available system? What brand would it be?
2. Anyone tried it before and compare with the original esseesse system

Thank you very much.

Looks a bit home made (or Magnetti Marelli) to me?

The only reason they put Cat's in the manifold is because they heat up quicker which helps lower EEC emissions as tested by the outdated test. The downside is that they do not flow as well as having them downstream, as you get better performance by having them downstream as you can then optimise the exhaust manifold design. Ironically this can also mean better mpg as less restrictive as well. The Trofeo Race cars had the Cat downstream as all race cars must have Cat's but are not subject to the same emission regs as road cars. Of course once hot all Cat's function the same so it's only going to be of any benefit emissions wise having it in the manifold on cars that are used on short journeys.

Can't help you on what yours is, but you may find a manufacturers name hidden somewhere on it, or could have been done by a local custom exhaust place who either knew what they were doing or had a good brief by the owner, or a bit of both to get what you have.

Thank you very much guys, let me jack up the car next week and dig out more about it.
Actually, from the de-cat down pipe, to the mid section and to the rear box, they look quite standard. Just wondering what is the donor car for the midsection.

The sensor setup looks fine to me. Petrol cars these days have a sensor before, and after the CAT to ensure it is doing it's job and to adjust fuelling accordingly.

It would be the same if the CAT was immediately in the downpipe instead of further down.

As long as there's no warning lights and emissions are fine, i'd be inclined to leave it as it is.