I have 2 left - $30 OBO
1 expire 6/2018
1 expire 11/2018
Discount: Valid for one annual Companion Fare from $121 (USD) ($99 base fare plus taxes and fees from $22 depending on your Alaska Airlines flight itinerary) when traveling with another passenger on a paid airfare. Valid for coach class only. Both passengers must be booked in the same itinerary, at the same fare, traveling together, and ticketed at the same time. Valid for round-trip or one-way travel. Multiple stopovers not allowed. Valid on published fares. Valid on published fares. Not applicable to Mileage Plan Award Reservations, Alaska Airlines Vacation packages, tour or contract fares.
No one else has seemed to discuss how it works but when I sold the last one I was given the itinerary they wanted booked and their info. I went and booked the itinerary in my account with my credit card. I forwarded them the receipt with all the information. They paypal'ed me the cost of the ticket plus what I was selling the alaska discount code for.