My understanding is that when a mould is made from an original, there is some loss of crispness. That might be interesting to investigate with the porcelain Smetterling.
It depends how it is done, if a positive master is made first then this can be adjusted to ensure a closer to the original but if done by hand the master would result in minute differences. Modern technology would scan the original and can copy through the glaze of pottery to the base. With pottery you can skip the positive and use a variety of materials but glass moulds must withstand the heat and the positive master has to be made first.