Hi AmyPink,
My guess is that it’s a private label made for Urban Mattress by one of the manufacturers they carry (possibly Sherwood) and not the actual name of a manufacturer but they could confirm this…
Mattress warranties only cover defects in the materials and they don’t cover the gradual (or more rapid in the case of lower quality comfort layers) loss of comfort and support that comes from foam softening that is the main reason that most people will need to replace their mattress. In other words warranties have little to do with the durability or useful life of a mattress or how long it will be before you need to buy a new mattress and longer warranties are more about marketing than anything else. If there is an actual defect in the material it will usually show up early in the life of the mattress. There is more about mattress warranties in post #174 here.
Knowing the quality/density and durability of the materials in a mattress is a much more reliable way to assess the durability and useful life of a mattress than the length of a warranty.
Phoenix