Before a glass goes into large-scale production, it should first be tested in individual cases for resonance in the coloured glass market. This is done under the label "Fuser's Reserve". If it is well received, the article has the best chance of becoming part of the standard range in the future. If you do not want to take the chance, it is best to stock up for a longer period of time with the usually small quantities available. It is a long way to the standard assortment.