Ok, it seems to have worked...
Creating the text file vers.ion, and writing it to mtd6
root@OpenWrt:/tmp# cat vers.ion
1.1.0 Build
root@OpenWrt:/tmp# dd if=vers.ion of=/dev/mtd6 seek=198673 count=11 bs=1 conv=notrunc
The TP-Link firmware said it's version was 1.0.0 (4555) (sorry forgot to make a screen shot), when I booted what previously claimed to be 3.0.3.
When I clicked the "Check for Updates" button, it said it was up to date, but
it'd still let me flash the most recent EU fw available from TP-Link.
now I'm back at
root@OpenWrt:/tmp# dd of=/tmp/a if=/dev/mtd6 skip=198673 count=11 bs=1
11+0 records in
11+0 records out
root@OpenWrt:/tmp# cat /tmp/a
1.1.0 Build
root@OpenWrt:/tmp#