Thieves also took four distinctive antique items from the Boer War and World War I.

Heritage Museum president Ewan Morrison said entry was gained by cutting through padlocks using bolt cutters.

"They stole some portable and attractive items and then broke into our laundry display by cutting the padlocks and smashing the window which separated that display from the museum proper," he said.

"They came in and just created havoc. They threw files around and all that sort of stuff - the office was a mess.

"We changed all the padlocks obviously and put stronger ones in. Ones that are a bit more difficult with a bolt cutter and three days they turned up again and the padlocks had been changed so they cut through the fence."

Mr Morrison said the stolen antique items are unusual and if spotted members of the public should contact the police.

"They were attractive and portable as well but they're not the sort of thing you'd pick up at Kmart or Target - they're a bit different," he said.

"If someone in the family or friends see people with these odd looking things perhaps they should get in touch with the Batemans Bay Police."

The museum is fitted with security cameras outside and Mr Morrison confirmed police are reviewing the footage from the two break-ins along with additional footage from neighbouring businesses. The thieves also bypassed a security system.

The damage to displays and equipment has left staff at the volunteer-run museum devastated.

"We were open last week but after the break in last week they smashed up windows in our war display, or our remembrance room, and that's forced us to close until a glazier can replace the stuff that was broken in there," Mr Morrison said.

"We're closed this week and that's a loss of revenue during school holidays. The replacement of the glass in the war room is about $1,200...and the replacement of the glass in the other area is of the same ilk, so a couple of thousand dollars.

"Plus the padlocks and the time lost and the volunteer stress."

The latest theft and vandalism at the museum follows a 2019 break-in and again in 2021, by the same person. On the two occasions external displays and a trailer were stolen from a storage area.

In 2023 Mark Ian Anderson was charged with 14 counts of break, enter and steal including at the Batemans Bay Museum. The alleged break-ins also took place at Pioneer Village Museum, Robertson Heritage Railway, Windellama Progress Association Hall, and Milton Millhouse Art Gallery - with the first incident reported in 2014.