First, can you take a better photo of the coin, one that can be enlarged? And second, can you provide weight and measurement? This info may help. I just looked through hundreds of images of Celtic coins and I could find no match to your coin. The closest I came were coins from Celtic Gaul and more specifically from the Suessiones who seemed to like using pellets more than others. Now this is purely guess work on my part. I'm not a Celtic coin aficionado and only own a few Celtic coins, so take what I say with a grain of salt, eh?
I got access to a Celtic coin database but very difficult and me too I own some Celtic coins but it is a very difficult matter. Me too I couldn’t find match it could be a Gauloise one or a German one. As there are a lot of hybrid one coin can have a obverse from a tribe and reverse from other tribe . With better photos and all information I can ask on one ancient coin forum where you got expert in Celtic coins.
I think what @Bing was asking for is ‘Full Image’ option when you post the pictures. It will be imbedded into the thread, full screen and can be enlarged. And this is the high tech picture setup I use with my iPhone 5s
If it is from Gaul you can try to look at this very big photo archive of Gaul Celtic coins https://www.cgb.fr/archive,gauloises.html
