Separate sound track
Is the strip completely brown, transparent with horizontal lines, with a small brown strip or an audio track? Then it is a separate sound track. In the early days of the film, you could not record sound and image at the same time. Besides, a separate sound tape allows to easily switch audio tracks, for example in the case of a film in different languages.
Is the strip completely white, transparent or coloured? Then it is a leader tape. This is an attachment that enables to put a film in a projector more easily. There is no audiovisual information on it. The strip consequently does not have any value. Unwind the tape enough to be sure there are no images on it, because a leader tape can be several feet long.
Is the strip black or does it have another tint on the back? Then it will probably be a film that is not yet developed by a lab or that is not yet exposed. In case of doubt, ask advice from a digitisation company.