16mm Mag dual stripe

[David Strelitz]

Some 16mm mag arrived this week and I did a "double take" as it had a dual stripe. The content was shot professionally for a private client Mid 70's.
It played fine the sound was fine but can find very little about 16mm Mag dual stripe. It was 4x3 so NOT Super 16 and besides I thought Super 16 was SepMag- hence the extra room for a 16x9 picture. Was the extra stripe used for sound or for Timecode? Can find very little about it.

[Maurice Leakey]

Some equipment and 16mm projectors could play back from a balance stipe, such as the Steenbeck editor.
16mm Mag Sound Recording Projectors - 16mm - Cinematography.com

[Joerg Polzfusz]

The main mag stripe normally protrudes a little bit from the film. Hence, without the additional balance track, the projector would have problems to have a proper focus across the entire image. So, on 16mm, there’s normally no sound on the second mag stripe. It’s only an aid for proper focus.

[Maurice Leakey]

Many years ago I worked in a Classic Cinema that had a small cinema converted from their old cafe. We had a 16mm xenon Eiki which could also play back magnetic as all the foreign Tatler Cinema Club films were dubbed into English using a magnetic track. None of the films had a balance track and we had no problems with focusing.
Similarly, I have a 16mm feature which just has the main magnetic track and I have no problems with focussing my Bell & Howell 1658.

[David Strelitz]

Thank you both for your replies. I am encouraged that it was most likely blank. Have I led too sheltered a life, as I have only ever seen single mag stripe 16mm ? 🤔