Image copyright Greg Pack Image caption Greg Pack is trying to trace who the people are in the photographs

When Greg Pack picked up an old wooden box at a car-boot sale, he had no idea what he was about to find.

A row of 18 glass pieces with smudged colours and ink were slotted into a wooden rack. They were photograph plates. He paid £4 for the box.

Before they went out of fashion in the early 20th Century, these glass plates were how photographers made negatives.

When Greg held the plates up to the light, their ghostly subjects appeared, decades after they posed.

"I realised I was looking at pictures than no-one has looked at for probably over 100 years," Greg, 70, of Canvey Island, Essex, told BBC News.

Image copyright Greg Pack Image caption Greg Pack picked up the box at a car-boot sale

As a former printer and someone who likes to repair antique objects, Greg had the skills to coax the images from the plates.

After trying to scan the plates using his printer, he eventually used his iPhone to photograph them. Using photo-editing software on his computer, he reverted the colours and managed to "digitally develop" the images.

"It was a bit nerve-wracking. I was thinking, 'I don't want to drop this plate, it's really old,"" he said.

What had been other-worldly figures suddenly transformed into men, women and children happily posing, unaware they would be rediscovered by a stranger more than a century later.

In one, six girls stand innocently looking at the camera, dressed in long white skirts and dresses.

Image copyright GregPack

Another photo strikes a different tone. Elegant ladies sit with furs around around their necks and extravagant headgear. On the far right, an elderly woman looks severely into the distance.

Image copyright Greg Pack Image caption A family portrait: The identity of the people posing is currently unknown

Standing in the same garden, a man wearing military uniform places his hand on a young woman's shoulder.

Greg explained that because it wasn't immediately clear which side of the plate to develop the picture from, some of the pictures were "back-to-front".

"It's hard to tell which side of the plate is the emulsion side, so the soldier's uniform is actually the wrong way round."

Image copyright Greg Pack Image caption Siblings, or possibly a young couple, pose in a garden

In another, a young girl laughs and plays with a man - her dad? Or could it be her brother?

Image copyright Greg Pack

Developing the mysterious photographs has produced more questions than it has answered.

The names of the people in the pictures are currently lost to history. It's not clear when the photographs were taken.

The clothes and accessories probably date to the early 20th Century, when glass plates were still used in photography.

A paper list of descriptions pasted on the inside of the box lid gives some clues:

"Old fisherman"

"Pigeons being let off."

"Balloon being inflated."

"Public washhouse"

"Old houses around Honfleur"

Honfleur - a picturesque port town in north-western France - has been a popular seaside resort for more than 100 years. Was this the family's holiday album?

Number five reads: "Henri Mabile" - a family friend? A relative?

Image copyright Greg Pack Image caption A list of the photographs in the box

After Greg's son posted the pictures on Twitter, on Monday, numerous theories have been advanced, including that the soldier's uniform matches one worn between 1901-1910.

Image copyright Greg Pack Image caption A lady smiles shyly for the camera

"There's a very good chance that someone will be able to track down their identity," Greg says.

He is thinking about taking them to the National Portrait Gallery in London, where experts can help with photo identification.

But for now, the family remains an enigma, glancing at the camera through time.

By Georgina Rannard, UGC & Social News.