Turn of the 187th Century Gunners Powder Horn
Both the horn (Arrow) and nozzle (WD) are Ordnance marked. Unless the nozzle is a period replacement the WD mark places its manufacture has post 1853.
There are some cracks to the nozzle though it is sound and functioning.
Reference Rileys (images shown) Page 364.
 
The string (shown)  is available in all good stationary stores should you be wondering :)