The article discusses the pin now on permanent display at the Leon Wyczółkowski Regional Museum in Bydgoszcz – an iron specimen with a large (D. 7.5 cm) disc-shaped head plated in bronze and a characteristic, broad flange (1.2 cm) (Fig. 1). Its short (6.5 cm) iron swan-neck shank is round of section, D. 0.4 cm. Its length suggests repairs made to the pin: the shank fractured and the stump was sharpened. The site and circumstances of the discovery of the pin are no longer known but the index card from the private archive of Józef Kostrzewski (Fig. 2) established the provenance of this artefact as Siedlimowo, Mogilno County in the Kujawy (Kuyavia) Region. It surfaced in a cemetery identified in 1892 by the parish priest Piotr Pacieszyński on a sandy dune found 1 km to the north of Siedlimowo (Fig. 3). The pin belongs to the inventory of a multiple-urn grave 3 (Reichert 1894). It lay inside the pottery bowl over the cremated remains together with An iron or a bronze needle. Like other archaeological objects the pin entered the collections of Historische Gesellschaft für den Netzedistrikt in fmr. Bromberg (now Bydgoszcz) where it was catalogued as No. 1056k. The pin from Siedlimowo belongs to a group of forms with a disc-like head with a flange, plated with bronze or gold sheet that are widespread in the Lusatian Culture and the Pomeranian Culture (Fig. 4:a). They correspond to type 2C in the classification of Sylwester Czopek (1992, p. 62–63, fig. 19), or to type Mrowino in the typology of Bartłomiej Kaczyński (2015, p. 26–27). In view of the characteristic rarely observed shape of the disc the pin has been distinguished as variant Siedlimowo. Three analogies have been found for the specimen from Siedlimowo (Fig. 4:b): two in cemeteries of the Pomeranian Culture (Jastrzębiec/Jastremken, Sępolno County – Amtl. Ber. 1902 [1901], p. 47, fig. 21; Nowy Targ, Sztum County, feature 123 – P. Fudziński, E. Fudzińska 2015, pl. XVII:6), the third in a hoard assigned to the Białowice Group (Cielmów/Zilmsdorf, Żary County – G. Kossack 1987, fig. 3c:36). Variant Siedlimowo pins, like type Mrowino specimens, apparently originated in the Białowice Group of Lusatian Culture. As a result of contacts between the Middle Odra region and Greater Poland during Hallstatt D these designs were adopted by the people of the Pomeranian Culture. Another trace of these contacts could be brooches with a decorative foot, type Wicina, pins with a bung-shaped and a cylindrical head, and pyriform pendants (M. Andrzejowska 1984, map 5:1–3; A. Lipińska 1966, fig. 26:2; Z. Woźniak 2010, map 1:b). The earliest pin classified to variant Siedlimowo comes from Cielmów and dates to phase Ha D2–D3. Similar specimens known from Jastrzębiec and Siedlimowo apparently date to the turn Ha D3 and “early LT A, which corresponds to the older segment of Karczemki phase (sub-phase B1 of K. Dzięgielewski 2016, p. 300, fig. 2). Their dating coincides with the chronology of type Mrowino pins, in fashion in Ha D3 – LT A (R. Mycielska, Z. Woźniak 1990, p. 40; M. Gedl 1993, p. 160; B. Kaczyński 2015, p. 31–33). The youngest would be the pin from Nowy Targ, grave 123 – it dates to the La Tène segment of Karczemki phase, which corresponds to Dzięgielewski’s sub-phase B2.