Thieves escaped with a haul of "irreplaceable" rugby shirts in the latest in a spate of three consecutive break-ins at the same rugby club.
South Wales Police are investigating the three break-ins and have not ruled out a link between them.
The burglaries, the first of which was on Saturday, is just the latest misfortune to afflict the club, located between Bridgend and Port Talbot.
Memorabilia was destroyed in an arson attack on the main clubhouse, in Castle Street, in August after a costly pre-season refurbishment.
The clubhouse's first-floor members' lounge was partially destroyed and other areas of the building suffered smoke and water damage.
The property's electrical system was badly damaged, as was its cellar and steel work on the stadium's stand.
The main clubhouse building was targeted on Saturday and Sunday when a quantity of alcohol and confectionery was stolen in twin break-ins.
In the third burglary, thieves forced their way into the building through the players' entrance door some time between Monday afternoon and early yesterday morning.
"The Rob Howley shirt in particular would hold a reasonable value for the thieves," said Pc Viv Price, of Maesteg police station.
"The shirts are irreplaceable and mean a great deal to the club and its members.
"I am appealing to anyone who may be offered any these jerseys for sale or has any relevant information to come forward"
Anyone with any information is asked to contact Pc Price on 101 or anonymously via Crimestoppers on 0800 555111, quoting reference 62130324707.