I have one of these that has no branding.
I uploaded a couple pics of mine to the gallery section here. Mine is nearly the same as yours except mine doesn't have an alarm clock, and records video to
3GP format, not ASF as yours does. It does play nearly all the verified good NES ROMs I've thrown at it, and many but not all of the ROMs which had not been verified as good. Mine didn't come with SD card nor games, but I have been able to use SD and MMC cards I already have which are FAT32 formatted. I tested it with a 128 MB MMC, and SD cards of various sizes from 64MB to 2GB and it read them all fine. Also, it doesn't support hot-pluging of SD or MMC cards. You do have to power off the device before inserting or removing cards. From what I can tell, the Sunplus chipset is based on a ARM9 core. I haven't gotten mine open yet (removing the four screws on the back still didn't allow me to open the case, will have to get a guitar pick and see if that helps), but I hope there are pads for a standard ARM JTAG port. That would allow reading and writing of the firmware.
The one problem I
have come up against is that, using the bundled Windows conversion software, I haven't been able to convert XVID or Divx movies into MP4 ASFs that it can play. The bundled
Sunplus video conversion software appears to be ffmpeg with a front-end to automatically make ASF files with MP4/Divx video @ 320x240, and stereo 16 bit uncompressed PCM audio @ 8k sample rate with little-endian byte order. The 3GP video files the player records with the video camera do play fine, however.