Eastern Sigillata B was an important ceramic ware of the Early Roman East, characterized by a shiny red gloss, micaceous clay body, and, in its first phase, epigraphic stamps on the vessel floor. Production was established in the Great Meander Valley in western Asia Minor c. 20 BCE, initially as an offshoot of the Italian sigillata industry, and flourished in the 1st and 2nd centuries C.E. Differences in the stamps and the appearance of the fabric suggest two phases, although the distinctions between them are not as straightforward as was once thought (Outschar 1996: 28, n. 79), and chemical analysis has found no differences between the clays of which they were made (Hatcher et al. 1980: 133–51, esp. 141; Kenrick 1985: 245, 508–9). Broadly speaking, however, the first phase (ESB 1) is characterized by finer fabric and epigraphic stamps, while in the second phase (ESB 2) the clay is less well levigated and name stamps are largely omitted or replaced by simple devices (e.g., rosette, asterisk). Evidence for an early, developmental period, predating the introduction of stamping and Italian forms, is currently under investigation (Fenn 2013; 2016: 53–54, 132–34). The first phase continued into the third quarter of the 1st century, with the span of ca. 45/50–70 seeing a transition (ESB 1/2) (Hayes 2008: 32). ESB 2 continued until at least the end of the 2nd century, if not later.
The distribution pattern of ESB 1 shows a heavy concentration in western Asia Minor (Lund 2003: 129, pl. 34:1), a good indication of its area of origin. Three further pieces of information combine to suggest that the main production site was located in the region of Tralleis (modern Aydin), about 50 km up the Meander Valley from Ephesos. limited excavation at Tralleis has recovered workshop waste that includes Eastern Sigillata B fragments bearing characteristic stamps (Takaoğlu 2006), and clay provided by a modern potter in the area of Aydin reportedly matches the clay of Eastern Sigillata B (Schneider 1995: 416; 1996: 189; 2000). It appears, then, that Tralleis was the (or a) main production site for Eastern Sigillata B, and its products were distributed overseas through the port of Ephesos, where huge amounts of the ware have come to light.
Versions of ESB vessels, very close in form and finish, were also made elsewhere in Asia Minor. It can be very difficult to distinguish these related productions from the ESB made at Tralles. One such local version is Sardian Sigillata, made at Sardis.
*this summary is from Susan Rotroff's article "Eastern Sigillata at Sardis: Evidence for a Local Industry," BASOR 380 (2018), pp. 133-204.