Da Ding Tong Bao / Blank. 25mm, 3.69 grams. Hartill -; Zhong Guo p.867 (rated as rarity 3 and listed at 2500 Yuans). SKU T525-50563
Some very rare cash are known in a different style, with a “triangle” Tong. These are often thought to have been a trial issue or a pattern of some sorts.