I was curious if there's anyone here collecting this kind of coins.
I do, but I think of them as Thracian coins. I know people have different views about this.
The Thracians dominated, well, Thrace, the region to the north and east of Greece bordering on the Aegean Sea and Black Sea. The Celts had their own small nation within Thrace, but only c. 279-211 BC before it was destroyed by the Thracians. The Dacians occupied lands further from Greece, north of the Danube River.
I believe that most of the imitatives that are frequently found in Bulgaria were minted by the ancient Thracians, who occupied land that is currently Bulgaria. The Celts occupied lands further west in current-day France, Netherlands, Britain, and so on.
Celtic coinage, particularly the issues that copied Philip II coins, differs from Thracian coinage in styling, with the former being fluid, curvilinear, and rubbery and the latter angular, pointillistic, and geometric.
I've acquired what I consider Thracian imitatives of Alexander the Great
style gold, silver, and bronze coins, Thasos Dionysos and Herakles tetradrachms, Mesembria war helmet coins, Istros inverted heads coins, Parion Medusa/Gorgon hemidrachm, Cherronesos lion
head hemidrachm, and Lysimachos Attic helmet bronze. You?