Here is a coin that I have but I cannot identify it. I'm pretty sure it's celtic. It's bronze and weighs about 8 grams. Cheers
Looks very similar to the Celtic staters found in Jersey. The obverse has that distinctive Channel Islands look. It may be a billon stater from there: https://www.wildwinds.com/coins/celtic/channel_islands/t.html The article below mentions that the coins are mainly from the Coriosolitae tribe of northern France, but some from other tribes too – like the Osismii, Redones and Baiocasses people. Your coin shows traces of silvering - could it even be heavily patinated silver? https://www.jerseyheritage.org/learn/jerseys-celtic-coin-hoard/