It looks like the rear bumper from the 6r (not the 6c) GTI or Blue GT; the reflectors in the pictures are the same shape as the space in your bumper, and the diffuser looks the same too.
If it’s a genuine VW bumper, I think the part number of the bumper is actually stamped into the plastic on the reverse side of the bumper - like in the last of the pictures below, so you’d need to remove the bumper to find it. (NOTE - the last picture isn’t of a GTI / Blue GT bumper so the part number isn’t the correct one for your bumper - I just included this picture so you can see how and where the part number is stamped / moulded into the plastic when the bumper is manufactured)
Here’s the rear of a Blue GT;
- 3E541EEB-D783-4C35-9DEA-DDB7FD7A9991.jpeg (89.86 KiB) Viewed 564 times
And here’s the rear of a 6r GTI (the 1.4 twin charge model, not the later 1.8 turbo 6c GTI which has a different bumper).
- F832BD55-CB2F-49FF-BE5E-E7FB8C9AF701.jpeg (303.51 KiB) Viewed 564 times
This is how the part number appears on the bumper (NOTE; this is just to illustrate the location of the part number -
it is not the correct part number for your bumper)
- 40666F9A-DE5F-40C5-99D9-2B77680C99C3.jpeg (51.32 KiB) Viewed 564 times