I don’t know what a potato seed looks like, but I’ve got some seed pods that are green and about 1/2” in diameter - like an unripe grape tomato.
Sounds like you have the pods containing the potato seed...check out the vid at post #92.
I guarantee you, in a SHTF situation with no food, you will find people digging up those Sunspot sunflower tubers and eating them as they ARE food and called Jerusalem artichokes. They do taste like water chestnuts and that's not a bad taste or people wouldn't eat water chestnuts. It is a nutritious food - since you know where they are, maybe you can make a business of selling them when people are starving.
As far as saving some regular potatoes for the next season, that is easier to do in states that have a genuine cold season to keep the potatoes alive/dormant. It's difficult to keep them until the next season in the south as it is warmer in the south. I grew up in real east Texas and Father could keep some under the house during the winter. Farther south makes it more difficult.
Info. on potato seed from Iowa State University:
"FROM: Iowa State University Horticulture & Home Pest News"
"OCCASIONALLY gardeners are surprised to find small, round, green, tomato-like fruit on their potato plants. These fruit are not the result of cross-pollination with tomatoes. They are the true fruit of the potato plant. The edible tubers are actually enlarged, underground stems. Normally, most potato flowers dry up and fall off the plants without setting fruit. A few flowers do produce fruit. The variety ‘Yukon Gold’ produces fruit more heavily than most varieties.
The potato fruit are of no value to the gardener. Potato fruit, as well as the plant itself, contain relatively large amounts of solanine. Solanine is a poisonous alkaloid. The small fruit should not be eaten. Since potatoes don't come true from seed, no effort should be made to save the seed."
If you ever grow a potato from these seeds you have to process, let me know how that turns out.
That is the potato seed pod.