I found this 2008 article also:
Printweek - De La Rue selected as a printer for Ethiopian bank note contract
This is the key part:
NBE floated an international tender in May this year inviting currency printers to produce over 1.1bn Ethiopian birr (Br) (£57m) in all denominations. Applicants included FCOF, which won the Ethiopian Birr contract three years ago.
FCOF had fallen under investigation from Kenya's Anticorruption Commission after it was implicated in a corruption scandal relating to Kenya's contract for printing electronically readable passports in the final years of Daniel arap Moi's regime.
Nonetheless, FCOF saw out the contract and delivered all the notes it was required to.
However, the current bid committee of eight, chaired by Alemayehu Kebede, the bank's modernisation and external relations director, awarded the printing of 10, 50, and 100 denominations to Gieseck & Deverient. The remaining denominations of one and five Br were awarded to Basingstoke-based De La Rue.
What I understand from this is:
1. All the notes from 2005 to 2008 were printed by Francois-Charles Oberthur Fiduciarie (FCOF)
2. G&D and DLR won contracts for printing different denominations, from 2008
3. DLR won the 1 and 5 Birr contract, G&D got the higher denominations
So if this is correct, we might say G&D never printed any of the 1 and 5 Birr notes, at least from 2005 onward.
I don't know about the situation before that.
An interesting thing I found:
When I look at my two notes (1 Birr) from 1997 and 2003, I can see plate differences on the obverse, have a look at the hairline and collar of the boy:

Also there are colour and pattern changes in the obverse background. The 1997 note is on the left and the 2003 note is on the right:
