Hello, J Brown.
Thanks for your interest. PCGS coins are allowed in US sets only. The decision to remove PCGS coins from World NGC Registry sets was made by Mark Salzberg, Chairman of NGC, in early 2012. In 2012, there was a significant expense to our company to expand the World NGC Registry to support both NGC and PCGS, and the result had been that we could not release new features that support collectors of World coins (such as integration with the World Coin Price Guide, Krause, and the Census). The different attributions and designations used by NGC and PCGS for World coins have compounded that difficulty. As such, only US PCGS coins are allowed in the NGC Registry.