These are from the Special Collections of the Oberlin College archives, a pair of antique African bellows from Angola. 

As you can see from the drawing, they would have been fitted with skin flaps lashed to the concave sides. 

Note that the drawing shows ten people working many small bellows to fire a bloomery furnace, rather than (as in Christopher Roy's video "Smelting Iron in Africa") one person working a very large pair of bellows. 

Here is a view of the nozzle. Note the absence of burn marks, indicating some kind of separation or insulation from the heat of the bloomery, probably a clay tube made at the same time as the bloomery itself. (NB: Such a tube would also provide some distance between the bellows-workers and the bloomery, lessening the risk of getting showered with sparks!)

And here is the interior, showing the openings to the twin tuyeres. Note the concave sides, which would have facilitated tying on the skin covers.

Top view:

Thanks to Special Collections Librarian Ed Vermue, and apologies for the poor lighting. 

Cool. Thanks. I had this discussion today concerning the bloom and it's operation.