Police said more than 300 items were taken from the safe at McTear's Auctioneers of 31 Meiklewood Road on the morning of Tuesday, January 17.
A man was captured on CCTV entering the premises at about 6:55am and leaving 20 minutes later. A member of staff arrived to start work at 7.30am to find the auction house unlocked, the alarm deactivated and the safe open.
Detective Sergeant Jane Lawson from Strathclyde Police is leading the investigation: "We have been checking CCTV as well as making extensive inquiries to trace those responsible for the theft of this jewellery. So far we are able to say that the suspect arrived wearing a black woollen hat, a high-visibility vest and dark clothing and was carrying a black holdall. A few minutes later a car with its headlights on arrived into the car park outside the auctioneers."
There was no sign of a break-in, said the police.
Much of the jewellery was due to be offered for auction by McTear's two days later. Other stolen items were scheduled for sales in the coming months or were on the premises to be valued.
Strathclyde Police have released a selection of photographs of some of the stolen pieces and have good images of all of the 300-plus items.
DS Lawson added: "I would ask the public, especially those in the jewellery industry, to take a look at them and contact Strathclyde Police (on 0141 532 2000) if they have been offered any items for sale."