Gang,
If such contributions are possible, then perhaps "shares" could be sold? You know, in the manner of all those past roads --- a spiffy, fill-a-greed (pun intended tongue in cheek), gold sealed, embossed, watermarked, neat o' piece of parchment suitable for framing?
And as such, could you give them real worth? Make them an authentic share of stock, vested by some economic instrument and therefore valuable at some time in the future for either redemption or continued growth in my retirement portfolio!
They'd probably be more valuable than dot-com stocks and at least going to a worth cause!
Later, Gary