Counterfeits:
Aramith Standard, Premier, and Super Pro models have all be copied. One of the brands copying the Super Pro balls is the Loto / Wu Yi Xin Kang brand. However, Loto also copies the box. They're probably all made at the same factory in China.

Here's a side by side comparison of Aramith to Loto:
Loto balls have slight differences on their 5's and 1's. The upper right tip of the 5 is a little fatter than aramith. The upper left of the 1 is fatter on the 10 and 12-15. The 11 ball seemed a little diff from the other 1's.
Weight wise, Loto's numbered balls are about 165.5 grams, which is about 3.5 grams lighter than Aramith. Their "whites" are the same shade as aramith. The colors are the exact same from brand to brand. The stripes are the same width. Sometimes aramith's whites surrounding the numbers seem to have a yellow/creme hint while loto's was the same as the whites outside of the numbering. Their six dot cue ball's red is a little brighter to the aramith six dot. The "whites" are the same shade as aramith.

I think someone comparing the 5's closely to aramith and weighing them all could be able to spot the fakes.
My recommendation for buying used Super Pro would be to:

1. avoid if the Super Pro box is not included
or
2. avoid if a red aramith logo or red triangle cue ball is not included, even though the Pro Cup sets would have only contained a 6 red dot cue ball

While they look the same, they're unlikely to perform and age the same.