@Disputatore @Badger
These are 50 year old film photographs, possibly made with different film stocks, possibly developed by different labs.
They've been digitised, and we don't know whether the digitisation is from prints (which may have been done by different printers on different paper) or from negatives, or from slide stock, and how old the film was when it was digitised and thus whether its deteriorated.
And we're all viewing them on screens with different characteristics.