Great photo .Thanks for the post .Photos are another world of colleting for me .
H R 17 was part of A K X .
The 19. Kav. Brigade had Oldenburg D R 19 plain black collar and cuffs and black hair bush
20. Kav . Brigade had H R 17 and
Hannover Dragoon Regt 16 ; plain yellow collar and cuffs ( yellow in B & W sometimes looks dark in old photos )
also black hair bush
so it could be either Dragoon regiment .I can't see if the helmet has the " Waterloo " banner
on it's front plate .Nor can I tell if the Oldenburg coat of arms is on the helmet front plate ?