When Lamine Zarrad was not at his job as a federal banking regulator in recent months, he was spending a lot of time at Denver’s marijuana dispensaries.

As a federal employee, he could not partake of the pot.

He was there, instead, to pitch the shops on a start-up he has been working on in his free time and is making official this week after quitting his job as a bank examiner at the Office of the Comptroller of the Currency, a division of the Treasury Department.

Mr. Zarrad’s start-up, Tokken (pronounced token), is one of several recently created companies looking to solve one of the most vexing problems facing marijuana businesses in Colorado and several other states: the endless flow of dirty, dangerous, hard-to-track cash. [Read more at The New York Times]