I had a offset handle SJ in a box like that, but smaller.
Weber initially told me it was a 77-78 based on the logo on the box.
However, someone on here said the offset handle was replaced in 74 with the center handle, so the latest it could be was '73. This made more sense as inside the box was a pamphlet that had a copyright date of, I believe, '73 (perhaps '72 though).
So, perhaps 72-78 or so?
Good luck.