Looking up the size of coins compared to shotgun gauges, I’m guessing the tale was dimes rather than nickles. Dimes would fit in a 12 gauge just fine. A half penny would need a 6 gauge, and a full penny would need a 10 gauge. I don’t know for sure, but I don’t think 6 or 10 gauges were ever popular shotgun sizes.
Looking up the size of coins compared to shotgun gauges, I’m guessing the tale was dimes rather than nickles. Dimes would fit in a 12 gauge just fine. A half penny would need a 6 gauge, and a full penny would need a 10 gauge. I don’t know for sure, but I don’t think 6 or 10 gauges were ever popular shotgun sizes.