This coin may look like plain edge, for one of these two reasons:
1 - They are heavily circulated and the reeds faded.
2 - The quality of mint is not so good and the reeds are struck too shallow.
Actually, two variants are recognized among Thai collectors:
1 - Large coat of arms (common, left end of the wand point the tail of พ)
2 - Small coat of arms (very rare, left end of the wand point the center of พ)
https://youtu.be/jVMNU2pgcxM?t=40s
According to the video, the amount of small coat of arms varient known is not more than 15 pieces.
Catalog editor for Thailand and Japan.
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