A British fashion designer said rediscovering one of her long-lost designs, which was found in an Oxfam charity shop after nearly 40 years, has been like “seeing a child” again.

Jean Pallant was told the orange coat with large buttons she had made at her kitchen table in 1988 had turned up in a donation bag at the Oxfam shop in Mill Hill, London.

“It’s like seeing a child. It’s lovely. I know every single square inch of it, and I’m absolutely amazed that it looks so new, and it feels new. Everything about it looks exactly as it did when it went missing,” she told the PA news agency.

Oxfam’s Mill Hill shop manager Marina Ikey-Botchway said she could tell the coat was a priceless item as soon as she saw it among a pile of fast fashion clothes.

“The very first second I saw the coat I knew this was something special, so I checked the label and after a quick Google found Jean’s email,” she said.

Sixties fashion model Penelope Tree chose the coat to wear in Oxfam’s Style for Change fashion show, in partnership with Vinted, as part of its Second Hand September campaign.

Pallant was part of the 1960s cultural revolution alongside her husband, Martin, and is restoring and curating a Pallant collection to give to the V&A Museum in London. She explained that she felt “sick” when, almost four decades ago, she discovered the coat had gone missing along with five other pieces, which have still not been found.

“When we retrieved them all, there were these pieces which I remember, of course, because they’re all my babies. These pieces were missing, and there’s nothing I can do about it,” she said.

She added: “I’d love those to turn up … One of them was a piece which is so important to us, which was made in 1972, I think. It was worn by me in a TV fashion show to celebrate Britain joining the common market and it was a beautiful white jumpsuit and jacket with little mink spots on it. I’d pay anything to get it back.”