I found some more information in this other article: https://www.dw.com/en/teen-discovers-first-ancient-greek-art...

""After we understood where it came from, I had the task of figuring out where this coin was found exactly. Fortunately, the boy was very precise and showed me exactly where he found it on a map. Then we went into our findings registration and found that this agricultural site was actually a well-known place," Henker explained.

Berlin'sMuseum for Pre- and Early History has been systematically conducting surveys on empty land in Berlin since the 1950s to determine where possible excavation sites might be.

In this particular spot, explains Henker, the upper layers of the soil were surveyed in the 1950s and 70s and again later. "Every time, they discovered a few distinct finds that made them say 'ok, there's probably more in the ground here'."

Over the years, fragments of ceramics, Slavonic-era knives and a bronze button have been unearthed on the site, as well as burnt human bones, leading researchers to conclude that this are was used as a burial ground dating as far back as the early Iron Age — and has been in use throughout the centuries."