Came across more information that may be relevant... still unable to unpack
these files.

fdisk -l app.yaffs = 
19 MB, 19442688 bytes
255 heads, 63 sectors/track, 2 cylinders, total 37974 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

file app.yaffs =
Linux rev 1.0 ext2 filesystem data (mounted or unclean),
UUID=26f91c60-f04c-4843-a8ec-b71ad911a723