This note concerns an enigmatic rendition of the mint signature on some groats, halfgroats and pennies issued under Robert II. On these coins the signature of VILLA DE PERTH is rendered as VILLA ED PERTH. This latter legend has been attributed to die-sinker error, born of familiarity with producing VILLA EDINBURGH mint signatures.
The representation of this anomaly across three denominations, involving multiple dies and many coins, suggests that the ED PERTH reading may have been intentional.
BNS Research Blog 
I read your well-researched article with considerable interest. Without in any way wishing to argue against your conclusions I would just like to point out one thing which I have come across in my study of the many die sinkers’ errors on reverse dies of the Edwardian sterling series. I have noted over the years instances of the same error which occurs on different reverse dies of otherwise the same class or sub-class of coin. It would seem to me to have been sensible when many dies were being produced at the same time to set out a line of new blanks and punch them out one character or feature at a time along the line of dies. This would minimize the constant interchange of punches for the die-sinker and make the process more efficient. Clearly any error would be repeated across the whole line of dies although, at the end of the work, the individual dies would be different.
This seems to me a possible explanation for the Robert groats in isolation. I think, however, that the existence of the same “error” for the half groats and the pennies is compelling evidence for your arguments. I cannot imagine a line of blanks having different denominations being punched at the same time.
Regards,
Denis
Thank you Denis for your interesting and instructive comments. Your observations of die sinker’ errors on Edwardian sterlings are, as you point out, contingent on dies being produced at the same time. Whether a production-line methodology was used to fashion the reverse dies of the Robert II groats is, like many aspects of the coinage, unknown. It is, however, a potentially rewarding line of enquiry. But for now, the additional occurrence of the anomalous reverses on half groats and pennies, tempts me to invoke ‘Occam’s razor’, and gratefully accept your support of my arguments as “compelling”.