In reference to the patent: US3281863
No—it is a utility patent.
Notably, design patents have a number beginning with "D" or "Des." (whereas this patent doesn't).
In addition, design patents only have a single claim referring to the drawings. However, this patent has a series of claims describing the patented construction, which would not be allowed in a design patent.
Ex-Examiner is correct - it's a utility patent.
The two main types of patents are design patents and utility patents. Design patents start with a 'D' in the number protect the ornamental design of an article of manufacture. They have a single claim that references the drawings (e.g., The ornamental design of an XYZ as shown and described." The drawings typically show the same article from multiple perspectives and the specification is extremely short (often one page).
On the other hand, utility patents typically have multiple claims, a long specification, and drawings that describe an invention in multiple ways.
The scope of protection of a design patent is defined by the drawings of the patent, whereas the scope of protection for a utility patent is defined by the wording of the claims.