The hurdles are sizable. For an exchange to fully function, a commodity has to have standardized specifications and some regulatory oversight, as products from corn to metals do, so everyone can be assured of exactly what they’re buying and selling, says Dale Rosenthal, who teaches finance at the University of Illinois at Chicago.

Weed comes in a very wide range of quality and potency and price. While there aren’t any futures contracts that trade on an exchange, there is at least one national gauge of the market, the U.S. Cannabis Spot Index compiled by Cannabis Benchmarks, a division of New Leaf Data Services LLC.

Amercanex buyers know the quality of what they’re buying because the exchange sends what’s sold on its platform to a laboratory for evaluation and shares the results, Janjic says.

But here’s the rub: Buyers and sellers have to be in the same state. The U.S. government regulates interstate commerce, and selling or possessing marijuana are federal crimes. So, then, is sending it across borders -- and Amercanex is an exchange for spot trades of physical purchases, not paper-only futures or options contracts. Right now, federal law is “the risk in this game,” Janjic says.

‘Really Fun’

In Colorado, purveyors were required until January 2015 to cultivate what they sold, and most still do. “The only way that I think you can really be successful is by growing your own,” says Bruce Nassau, the CEO of Tru Cannabis, which has five stores. “If you’re buying from a wholesaler, you’re screwed.”

In Oregon and Alaska, merchants are allowed to use their own raw materials, but Washington legalized in 2014 with a law forbidding retailers from doing so. “In a system like that, exchanges become more useful,” says Adam Orens, the founding partner of the Marijuana Policy Group.

Amercanex started in July 2014 with 20,000 seats, though it has retired about 8,000. The seats began selling for $2,500 each and are now going for $10,000, Janjic says; 7,000 are are still up for grabs.

Dixie Brands Inc., a Denver-based maker of tetrahydrocannabinol-infused products, bought a seat last year, and has an equity stake. Amercanex will help distribute its goods more efficiently, says CEO Tripp Keber. “You’re starting to see some other players come into the market, which I think is a strong endorsement.”

For McNally, who’s on the three-member advisory board and owns a seat, being part of a brand-new sector is exciting. “It reminds me of when I first started,” he says, recalling his days as a Hang Seng Index options trader in Hong Kong in the ’90s. “It’s really fun.”