Design Patent on Open Ended Wrench, Functional or Ornamental?

The USPTO recently issued US Design Patent D859,108 covering a wrench, which is shown below.

Every part of this wrench is shown in broken lines except the U-shaped mouth working portion that is for engaging with another part, such as a nut, bold head, or the like. Therefore, the U-shaped part, shown in solid lines, is the only claimed part of the wrench.

I wonder whether the curvy design of the U-shaped part is functional. Design patents are to be directed to ornamental designs. So, if a design patent is directed to a design that is primarily functional, the patent can be invalid.

However, the standard for invalidating a design patent as directed to primarily functional matter is stringent. See Ethicon Endo-Surgery, Inc. v. Covidien, Inc., 796 F.3d 1312, 1328 (Fed. Cir. 2015). The Federal Circuit Court of Appeals has said that “[w]hen there are several ways to achieve the function of an article of manufacture, the design of the article is more likely to serve a primarily ornamental purpose.” It also said, “[I]f other designs could produce the same or similar functional capabilities, the design of the article in question is likely ornamental, not functional.”

Here, I don’t know whether the curvy design of the U-shaped part imparts a functional benefit, or, if so, whether other designs could also achieve that function. However, it is interesting that the only claimed portion of this wrench is the working mouth portion that is for engaging with another part, such as a nut, bolt head, or the like.