May be of Hellenistic origin when cistern system went out of use.
For a general note on the cistern see Nb. ΟΕ III, pp. 246 ff.
Objects from B 586 various depths (no subdivision): S 2324-S 2330,
P 34894, ... Late 2nd-early 6th c. A.D ... Agora VII, p. 226 ... Agora XXXIV, p. 182 ... Agora V, p. 125.