Acacia melanoxylon is a very common street tree in my city. It's considered the "sister species" of Acacia koa, a Hawaiian species prized for it's wood. I understand the thinking is that Acacia melanoxylon (or it's ancestor), made it from Australia to Hawaii, where it diverged slightly. Still, the wood is good enough that it can be used for everything Acacia koa is used for, and that includes surfboards.
Here's a clump of seedpods + seeds from a local tree.
And the seeds, removed from the pods:
Here's a seedling that came up as a weed on a redwood tree. Note what appear to be dimorphic leaves:
The finely divided ones are actually leaves, and the immature ones. They transition into phyllodes as the tree grows.
I guess it's odd that it's "melanoxylon" = "black wood", growing on a redwood.
Anyway, I'll send the seeds on my stamp and assume they are far too tough to be crushed by USPS. It think they need nicking/soaking and maybe also hot water to germinate. I'll look it up.
If more than one person is interested I'll decide by random number generator.