not only is that type period, it is recognized as frontrunner for the first truly mechanical only movement.
The man who was to be come Pope Sylvester II had what is acknowledged as the first completely mechanical clock in 996 CE, and it supposedly had this radial pin design. But that is all buried in my notes as to the quote source.
However, to give you the reference you are desperately seeking:
1327 CE - Richard of Wallingford ("Tractus Horologii Astonomici") wrote on a tower clock he built for the Abbey St. Albans that it had a "strobe escapement", two wheels on the same axle with alternating radial teeth/ verge suspended BETWEEN them, with a short cross piece oscillating as the wheels rotated past. (no currently known period examples exist, primarily because they lost as much as several hours a day, and were quickly changed over in the 1600s to the vertical pendulum because those lose only minutes a day.
Part of the problem is that a) the first treatise on clock making wasn't until 1364 when the son of a clockmaker expounded upon his father's work, and b) as stated above, they were all changed over to the vertical pendulum in the 1600s.
So,Good Master, since I seem to have gotten you hooked, your other research terms should include "escapements" and, oddly, "engines".