Factor banka got the shares as collateral for a now delinquent loan taken out by Primorje Holding, the MBO vehicle.
The asking price is EUR 1.3m and the auction will be held in Ljubljana on 2 April.
The move comes just as overindebted Primorje is scrambling to secure a capital injection by the end of March in order to avoid receivership.
Primorje, trade unions and even the opposition have asked the government to come to the rescue considering that redundant workers would present an immediate burden on public finances.
But the government has made aid conditional on existing shareholders "extracting themselves from the story", as Economic Development and Technology Minister Radovan Žerjav recently told the STA.
Žerjav has also suggested that any bailout would have to be indirect, presumably through the state-owned SID development bank, as there is simply no extra money in the budget.