Purpose. We describe the technology of thin-walled casting of the «blind» bronze celt bush, which was different from the Bronze Age celts. This technology had been developed in the Early Iron Age in Siberia. The celts we studied differed in the way of fastening the stoppers on the core, as a result of which they had through holes on their wide edges. Due to peculiarities of the casting technology, the core of the celt was almost always destroyed after casting. Therefore, morphological analysis of this part of the mold is impossible. The analysis of museum collections and published materials made it possible to reveal a variety of incisions, protrusions, incisions, etc., on inner walls of the celt bush, which allows us to expand our understanding of casting production and reveal some morphological features of the core. Results. Dozens of diverse features, 6 types of internal design of the bush and more than 20 variants of making cores were distinguished by the analysis of more than 300 items of bronze celts from the territory of Western and Middle Siberia. Morphological analysis is used as the basis of classification as it formalizes the characteristics of the object under study. The classification scheme is divided into 4 taxonomic clusters (cells): group, type, subtype, variant. The lower stage of the classification pyramid contains the maximum set of options for the internal structure of the bush. There are five special features of the celt bush among the products of the Early Iron Age from the territory of Siberia: «spiked» protrusions (at the bottom of the bushing), transverse partition, «corner», «skids» located on wide walls plus a combination of features. For several specimens of the celts, several techniques were noted applied at once (depression + incision). This allowed us to distinguish the «combined» method for the design of the core. Conclusion. We managed to isolate features typical for a certain territory or having a territorial character. Such features as «corner» and «spiked» protrusions are found only on the products of Middle Siberia. We identified the continuity of some technological methods used in manufacturing a hollow bush. Thus, the transverse septum, which is fixed as a feature of the West Siberian metallurgical tradition, appears on Tagar products. Using the typology presented, we can draw conclusions not only about the presence of established traditions of bronze casting production in a certain region, but also about the existence of masters who used non-standard approaches in manufacturing. This, in turn, is a great marker. The ratio of the availability of products with a «clean» bush and the presence of additional elements in it does not exceed 10%. This phenomenon seems to us not only a cultural phenomenon, but an overall technological response to a specific need or problem related to manufacturing technology.