I have a round of what I suspect is 8
I have seen brass cases which are now in very poor condition showing a copper color as you note on your example. As to the correctness of the round or the missing headstamp letters, sorry.
The “C R” intertwined is actually “GR” which is the Georg Roth monogram, and the round was made in 1915.
I suspect it is a perfectly original wooden blank that has perhaps been buried and the copper has leached out of the brass.
From the headstamp I’d say this is more likely to be an 8x56mm Kropatschek blank made, as Tony say’s, by Georg Roth. The headstamp would most likely read 1905 and it would have been supplied to Portugal. The Portuguese designation of this round was ‘8mm Cartucho con bala simulada m/89.’
I can confirm that I do have a blank with the 1905 headstamp so it certainly does exist. I’m short of time at the moment but will post a picture of the round in question if required however I suggest the question has been answered satisfactorily already.