A couple of years ago, the Celtics turned their office on Causeway Street, near TD Garden, into a pseudo museum detailing the franchise’s history, with pictures and memorabilia covering nearly every square inch of space.

And down one hallway, all the Celtics logos dating to the team’s founding in 1946 were splashed on the wall, each carrying the story behind its origin.

Those stories sparked an idea for something new with a touch of the past, and after 18 months of work, that idea will debut this week: a new alternate logo.

Created in-house, the logo, which is known as the “Lucky Alternate,” pays homage to the early 1960s illustration created by Celtics patriarch Red Auerbach’s brother, Zang, a former editorial and sports artist for newspapers in Washington.

It features the classic image of Lucky the leprechaun spinning the ball on his finger, only in white silhouette against a green backdrop, encircled by the words “BOSTON” and “CELTICS” in white.