My nano was delivered from UK although the e-bay listing quoted source as China.
The files were delivered as attachments to an e-mail from someone called guojun Ding from goodness knows where ??
Interestingly the Benf files appear to be accepted by the nano as they show as RDY after copying them into it (just like the quad) but on reboot it still has the previous app running.
I tried messing about with file names and upper and lower case as the files from guojun Ding were in capitals and were just LIB_V225.HEX and APP_V260.HEX I changed the benf files to this type of filename and they then wouldn’t load, just came up with ERR instead of RDY. Don’t know if this casts any light on the problem or just adds confusion.