I have now found him the references are very confusing.
DCM Nig Gazette 12/10/16, p. 533 (Cameroons: Gen citation Sgt. NR)
Bar Nig. Gazette 10/10/18. P. 396 (German East Africa CSM 4NR)
For taking up his present duties on 17th Sept in succession to a C.S.M. with an exceptionally fine record and in addition having the disadvantage of being a new comer to his present company, he had a difficult position to fill during an important period, but by constant disregard of personal risk and by sound judgement in action, continual hard work and fine handling of the men he rapidly established himself and his services and example have been of the greatest of value.
M.I.D. Cameroons: L.Gaz. 31/5/16 (Dobell's despatch) 127 DCMS were issued to the WAFF during WWI with 5 First bars and one Second bar.
So while the medal is not unique, it is extremely rare.
As to other entitlements difficult to say obv. WWI, given he was a Sgt. in 1916 quite possibly entitled to a pre-war AGS.
All the best,
Paul