Ankh

It is unlikely that the Egyptian shadow clock was called such.
Other names it has today are the L, due to the missing cross bar,
the T, after its restoration based on Borchard and the Green Schist
Shadow Clock by the one we have. We remember here that the
Egyptians had Sun Gods and it is plausible that instruments used to
measure gods path amongst the heavens were given a higher status
than the average instrument. This judge of Sun god's, this marker
of the seasons, the crops, the pagan ceremonies, this shadow clock
has the god of the day upon it. Thutmose III.

Now instruments are often known by their use, what they are
used for. Like Hammer and Nail. So it is possible that these
shadow clocks taken on the circle of the sun, or god.

This T section, with a circle on top fits the shape of the Ankh.
The symbol that Egyptian priests are seen carrying, as depicted
on temple walls.

It is thought that the T section may represent the sun's
rays or that the circle is the sun or the sign of the female.
All combine when we consider that Egyptian religion considered
the sun's birth or rebirth was tied with sunrise and spring.

With this there can be some blurring between the symbolic
Ankh and the shadow clock that measures the sun.
Some Ankh's could be clocks, some small clocks could be Ankhs.