They are usually ones where there are few clues to where they were taken with no date and often shed no light on the identities of the people who stare back at you.
And that is pretty much what we have here from a collection of images which belong to David Kennedy.
The originals were 4 by 5 glass negatives and date from sometime around the end of the 19th or the beginning of the 20th century.
Some are of street scenes, others of men and women at work and include a fair number showing life on board a selection of working ships.
They range from causally posed scenes to ones where the photographer has caught his subjects fully occupied and perhaps unaware that they are being photographed.
In the first the mother is staring down at her baby and in the second she smiles back at the camera while in both the photographer is caught in the mirror.
There are no clues as to where they were taken but in one there is a reference to Ostend and a few carry the names of hotels and restaurants, added to which there is a very distinctive church all of which should help.
And so over the next few weeks I shall feature more of these images and try to get closer to solving their mystery.
Pictures; by courtesy of David Kennedy