The replacement for the second failed Sony SR-64UY MicroSD card arrived:
The previous cards were made in Korea, but this one came from Taiwan with a different serial number format:
The tiny letters on the front identify it as an SR-64UX, but I haven’t been able to find any definitive Sony source describing the various cards; their catalog page listing cards for digital still cameras may be as good as it gets. This one seems to have a higher read speed, for whatever little good that may do.
It stored and regurgitated the usual deluge of video files with no problem, which is only to be expected. This time around, I checked the MD5 sums, rather than unleashing diff on the huge files:
cd /media/ed/9C33-6BBD/ for f in * ; do find /mnt/video/ -name $f | xargs md5sum $f ; done 11e31c9ba3befbef6dd3630bb68064d6 MAH00539.MP4 11e31c9ba3befbef6dd3630bb68064d6 /mnt/video/2015-07-05/MAH00539.MP4 ... snippage ...
It now sits in the fancy plastic display case that the HDR-AS30V camera came in until the previous replacement card fails.
The Smell of Molten Projects in the Morning 
Since getting a couple fakes, I too have been testing every single flash-card I buy. I now use “f3”.
As easy as: f3write /media/ed/9C33-6BBD/; f3read /media/ed/9C33-6BBD/
(http://oss.digirati.com.br/f3/)
What I still miss is a tool that lets you write to the flash controller directly. Apparently these tools exist on some gray market, mostly to create fakes in the first place.
Looks great to me!
I don’t have any counterfeit / defunct cards right now. The f3probe test reports the known-good 64 GB Sony card as good, so the code passes the dipstick test.
Thanks for the pointer!