As padi mentioned the stitching on the label is very poor. Gucci would never sell an item with stitching like that. The base of the label also appears poorly cut in the photos. Is the back of the brown Gucci tag white card as appears in the photo. ? I would expect Gucci would use higher quality card in the tag, although some of their boxes have printed exterior with gloss white card on the inside..

With all fashion labels, the first thing to look at is the stitching. Is it completely uniform ? even on tight corners etc. Are the seams well finished or slightly ragged with irregular stitching ?  Top labels have perfectly uniform, tight stitching, even where it is difficult to see. Knock offs invariably have defects in the stitching, stitched lines not perfectly straight, irregular width between individual stitches, particularly in tight spots and uneven curves in stitching on tight corners.

The fittings such as zip handles etc. on knock-offs often have moulding marks or seams and the plated finishes wear easily, showing base metal or plastic. Zips on genuine articles are very high quality and operate with velvet smoothness. Knock offs often have glue lines visible on seams etc. on purses and bags. You will never see glue lines or marks on the real thing. The genuine article usually holds its shape perfectly, while cheap knock offs can sag and distort over time.

The letters on fake labels are not always printed with perfect uniformity and sometimes just look cheap.The genuine article uses high quality printing techniques on quality card or fabric. The edges of fabric tags on the genuine article are uniform and well finished, without any ragged or rough edges.

Basically if you can see any inconsitancies of any sort on close inspection, it is probably a knock off..