Burglars punctured a 2ft (60cm) hole in the wall of a local family business before getting away with tweed jackets.
Police were called to the V&J Knitwear store in King's Lynn in the early hours of Tuesday to discover the hole at the back of the property.
Store sales director Richard Waterfield said more than 100 distinctive tweed items were taken, as well as workman's harnesses and cash from the till.
Other jackets will also have to be thrown away after being dropped in mud.
Mr Waterfield said: "It's just very worrying people can come into your business and take what they haven't paid for."
He added the support from the community had been "tremendous" and they have had offers from local businesses to rebuild the wall.
The alarm had initially been set off at the property in Hamlin Way at about 23:00 GMT and Mr Waterfield went to check on it but could not find anyone, believing a mouse had set it off.
However, the alarm went off again and police were called at just after 01:00 GMT.
Mr Waterfield, whose business will celebrate its 50th anniversary next year, said the tweed items taken are of a distinctive Greenbelt brand and not readily available.
He also believes the theft may have been carried out now because it is close to the shooting season.
One of the shop's employees, Becky Nichols, posted pictures of the damage on Facebook, which have now been shared thousands of times.
"We just want to make it awkward and give them a sleepless night or two," said Mr Waterfield.
Norfolk Police said they were investigating the case as a burglary and are appealing for witnesses.