The all-stock deal is broken out into two parts: First, existing MakerBot investors and executives will receive 4.76 million Stratasys shares as an upfront payment. That was valued at $403 million when the acquisition was first announced, and now is a few ticks higher at $406 million. The ultimate value, however, won’t be determined for awhile since recipients are prevented from selling these shares until three months after the deal closes.

Second, there are another 2.38 million shares tied to performance-based milestones through the end of 2014. If these earnouts are achieved, this $200 million+ worth of shares would go to MakerBot investors, executives and non-executive employees.

All of this represents a massive return for MakerBot’s venture capital backers. The company was seeded in April 2009 before raising Series A funding in the summer of 2011. That deal was reported at the time to be for $10 million, but Fortune has learned that it ended up raising $13 million at a $48 million valuation.

In other words, we’re talking about a return north of 12x in less than three years (assuming the full earn-out comes through and the stock doesn’t fall too much).

Foundry Group led that Series A, and included such other firms as Bezos Expedition, RRE Ventures and True Ventures. At the time, Foundry’s Brad Feld explained his views on the future of 3D printing:

“I think 3D printers will be commonplace in a decade and will be a broad-based consumer product. I don’t know if it’ll be integrated with a 2D printer as the technology is very different, but it’ll be fun to see people try. I’m especially excited about a self-replicating 3D printer – won’t that be cool. It’s just another step in the process of the machines taking over.”

Feld and several other MakerBot VCs declined to comment for this piece, saying they’d prefer to wait until the acquisition closes.

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