Hi Fab1972,
Dear member of SanDisk Community, welcome.
Well, friend, as you suspect (it’s also very cheap?), is fake.
International Protocol of the SD Association , it’s for all brands, and 64 GB, is SDXC only.
For more detail on this topic, you can check here: https://www.sdcard.org/home/
I guess that it’s a microSDHC 4GB, to which they added 6, or something similar.
If you bought it, then can make the following tests and verify:
1- Format with (free): USB Flash SD Formatter 4.00, http://filecloud.io/jqtu1byc
Also you can try, with three portable utilities (free), whether they are fakes:
2- USB Flash H2testw 1.40, http://filecloud.io/jl4fhn9b -It’s the classic utility, but for 64 Gb, it takes ~ 4 hours.
3- USB Flash FakeTest 1.09, http://filecloud.io/n074g3x5 -It’s similar, but has a quick option, and takes minutes.
4- USB Flash ChipGenius 4.00, http://filecloud.io/rqa7etmv -All internal data, of your UFD.
Luck, and then you tell us, what happened, please.
Regards, Alfred. (Google translated)