I would advice you not to waste money on this kit. There are indeed many fake products out there. If you are looking for something diagnostic, the gold standard is PCR, not antibodies. I understand your worry, just that there aren't a lot of quality assurance on products claiming themselves as rapid tests.
Has anyone walked into the HK gov't general outpatient clinic or hospital and asked for an antibody test?
Like the OP - I'm interested in knowing if I have LIKELY had or not had it in the last few months so a PCR test will NOT be suitable - only an antibody test.
I tried to get into a couple studies offering free antibody testing, but they filled up too quickly (within minutes or hours).