Please Help with Ancient Coin Identification ~ It is a Strange Piece

numisma

A customer asked me to help identify an ancient coin. Usually I do okay, but this one really has me stumped. It has elements of an ancient Greek drachm, but I have never seen such design elements. The weight is 5.85 grams and the dimensions are roughly 16.5 mm X 18.5 mm oblong. It is silver and the fabric tells me that it is a genuine antiquity.

What do you think? The main identifying factors are the four dots, one each within neatly engraved quadrants. The obverse design appears to be a figure standing with a shield, but that's a guess. I asked another local dealer and he said it could be ancient India, but he also said to look into Celtic coinage.

Any direction or advice is greatly appreciated. Thank you!