RFX error ?

[Eirestan]

Is this an error or is it just a die fill ? 

Reads RFX instead of REX. I can't find it in the Spinks guide or much about it online. I think the month may be the September variant with the stop after Sept and after XII but not 100 % sure of that. 

[Paddy]

Welcome to the forum.

I am no expert on the Gun Money, but it would seem likely that there are many die faults and die fill variations around as they were struck largely on campaign. Even the regal coinage from the 1690s has a huge number of variations.