It says it right on the bar: 'fine gold'.
LOL but if i was a noob and i was buying it, who would i trust? how would i check quickly for myself

Here is a way:
You weigh it (on an accurate scale), than you measure the volume by putting it into a finely graded measuring cylinder with some water. Note the increase in volume when adding the gold bar. The volume for one kg gold should be 51.86 cubic centimeters (ml).