A gold sovereign is a highly regarded and historically significant coin, typically minted with meticulous care to ensure high quality. Given this context, it is extremely rare to see lamination errors in gold sovereigns for several reasons:

1. Purity and Quality Control: Gold sovereigns are struck from high-purity gold (22 karat or 91.67% pure). The quality control during the minting process is rigorous, with strict standards to ensure the purity and integrity of the metal. This reduces the likelihood of contaminants being present in the alloy, which are often the primary cause of lamination errors.

2. Manufacturing Precision: This sovereign was minted by the Royal Mint,  known for their precision and high-quality manufacturing processes of sovereigns. These mints have stringent procedures to detect and eliminate any planchet defects before striking the coins.

3. Material Properties: Gold, being a noble metal, is less reactive and less likely to contain impurities that could cause lamination errors. Unlike some other metals, gold does not easily form oxides or other compounds that might lead to such defects.
   
   In summary, this coin is exceptionally rare and I have only previously seen one example of a sovereign with a similar error. Whether you are a sovereign collector or like me, tend to favour the strange and unusual, an error sovereign is something that very few collectors have  the privilege of owning.
   
   Note: this sovereign also has a die crack which runs from the head of the horse out to the rim of the coin. Perhaps this coin could be considered a "unicorn" in more ways than one!