The announcement, made as part of an otherwise upbeat release of a positive set of results, stated that the directors remained confident that the sums owed would be paid in full, but that they were taking legal advice in order to protect their position.
They also announced that they had not released the coins purchased by the Qatari collector connected with the non-payment. "We will issue further updates in due course but, as stated above, we will continue to retain the coins until such time as payment is received," they reassured shareholders.
The auctioneers were able to point to strong sales at Coinex in September, together with a world record for an English or Australian coin - the £650,000 taken for the George V 1920 Sydney mint Sovereign on September 27.
The share price closed 1.02% up on the day at 188.9p.