Mandarinquat is a fairly cold hardy citrus that can survive down to 14 F, it's more hardy than Calamondin but less hardy than kumquat
mandarinquat = mandarin x kumquat
skin is moderately edible, not as good as kumquat
interior is more edible and more flesh than kumquat
3 seeds, 4 dollars (seeds will go out, might send you the bill later)
limited time, probably ending in next few days