Nice! You therefore are probably already aware of the single letter that was found inscribed under the dial right in the center of the underside? There is a letter ayin carved into the underside, right in the center of the dial.
Qumran Sundial - Madain Project (en)
The top design therefore seems to reveal, with a high probability, the form of the most ancient version of the letter ayin, the eye, as also seen in Sinaitic rock inscriptions. This in turn appears that it may also be a hint at some background context for the parable or idiomatic saying in Matthew 7:4-5, for with a gnomon placed into the hole in the center, the eye would have a stick or stake in it. It can also be symbolically viewed as a throne-room with a stake at the center. Note also that the dial even looks like a catch basin for water, (as you know the eye is also likened to a fountain and ein, the very name of the letter, is either an eye or a fountain).