It isn't in the catalog, it's a special for a Draper Loom....
(DS - Draper Service wrench, I suspect)
There are at least 4, probably 5, you have (probably) the only flat one, there is an offset, and a T-handle, and something else I forget offhand...
Textile wrenches are really badly documented :(
DS-3 is more clearly a Textile wrench...