Dave, thanks for these interesting images! Did you compare these to the S&B cartridges of this time? The PA looks very similar.
Maybe their machinery and supplies came from Czechoslovakia?
There are also 7.62x39 with similar headstamps whcih I so far suspected to be Ethiopian but there was no big proof to it other than the PA color.
And then there is a 7.62x54R with hs:
Also I found that the Ethiopian 7.62x39 packing is in boxes in a 2 rows of 10 cartridges. These we know typically from Czechoslovakia and still today from S&B.
And it seems at some point they have stopped using headstamps. Or at least on those cartridges for export as those are shwoing up in the hands of all sort of armed groups of which we would want not even having sticks.
To my understanding all their SAA is made by Homicho (as per appearance).