The principal deposits in which the objects were found are located in the central part of the sanctuary, in the area surrounding the Temple of Poseidon.
The area of the temenos must have been a sanctuary well before construction of the first temple to Poseidon in the 7th century B.C. Burnt animal bones and ceramics from the beginning of the Early Iron Age appear in primary deposits near the Long Altar and in redeposited fills from the Early Stadium. Some of the oldest metal objects, such as the Protogeometric straight pin 177A, belong to that period. The 8th century witnessed more numerous dedications of jewelry and tripods, although none of these was recovered from its original location.
The depositional picture is the same for the Archaic period. Most of the metal objects were found in deposits related to the destruction and subsequent reconstruction of buildings, especially the Archaic and Classical Temples of Poseidon. The former burned between ca. 470 and 450 B.C. and was replaced on the same site, although on a larger scale, by the latter. The Classical Temple in its turn was damaged by fire in 390 B.C. For the chronology of objects associated with the temples such a context provides a terminus ante quem, but it is of little help in indicating the date of manufacture. In many cases, particularly when determining whether something belongs to the late Archaic or the Early Classical period before ca. 470-450 B.C., Professor Raubitschek relied on comparisons with objects from more securely dated deposits at other sites.
The three major areas on the periphery of the temenos that contained objects from the Archaic Temple as well as materials related to activities taking place in the vicinity after the fire are shown in hatching on a restored plan of the sanctuary around 400 B.C. (ATplan). The northern deposit was created to support the Corinth-Isthmus road, while the eastern deposit formed an extension of the sacrificial area east of the Long Altar. The third deposit filled a rock-cut water reservoir (ca. 5 m. in diameter and 19.75 m. deep) located outside the southwest corner of the temenos (Trench H, also designated the Great Circular Pit). It was abandoned and filled in by the end of the 5th century B.C., but the uppermost levels underwent some disturbance in the Roman period.
Within the Archaic Temple the pronaos held what appear to have been remains of the temple treasury, including objects of gold and silver, but also many scraps gold leaf, fragments of silver, coins, and other items of value. The other metal artifacts from the temple, although largely Archaic, came from areas (the cella, for example) where there was an admixture of later material. None of the deposits was sealed, and it is not always clear from the excavation record whether an object was retrieved from a purely 5th-century context or there had been later intrusions.
"Isthmia, Volume VII, The Metal Objects (1952-1989)", by Isabelle Raubitschek