Anyway, as it looks like a 104th IR number, I ran AKE through lists of men in the unit and nothing turned up. However the 104th is one of the very few units in WW1 that actually had a roster of men by serial number - so I had a frieind with this document run the number 71686 (and 71688 just in case) thorugh a listing and it came up negative.
Its possible the guy was 104th and somehow did notget on the lists (such as a very quick transfer out),
That neither 86 or 88 were listed makes me think that those numbers were "left over" from a block assigned to the 104th and given to men who did not fit into the main scheme of the system at that time.
Sorry, I tried.