That looks like the front box to me (between the cat and the back box).

The car's got to be at least ten years old. What's its history, how long have you had it, has it a misfire?

It doesn't seem too corroded. Did it backfire? maybe a blocked back box?

I had a petrol N16 Almera for nine years and sold it on when it was eleven years old, still with the original exhaust. Yours could still have been the original.

I had one car where the back box collapsed internally. The perforated tube rusted away allowing the wadding to partially block the exit. That became very sluggish and wouldn't rev. The exhaust note at tickover changed from a pulse to a continuous blow.

Let us know what your result is.