Sometimes when I purchase vintage film equipment from auctions, estates, etc., the cameras or boxes contain old 8mm or 16mm film reels shot by an amateur from decades ago prior to video. No photographer or owner is identified on them and are original positive footage, not negative, therefore most likely no other copies exist. Most of the footage is of landmarks, cityscapes or wide shots of people that cannot be positively identified.
Does the 75-year Copyright apply or because no ownership is known, does it fall under a different statute of limitations?
Shorter question: Can I legally use this footage professionally in projects or to digitally archive as retro stock footage for sale?