Michelle,
To add to the confusion rather than provide a clear answer as to where it was made, in the book Dartington Glass, The First 20 years, these limited edition Churchill plaques are photographed on page 65 noting that they were made in 1974 possibly in Sweden and finished at Dartington. I have seen one before on e-bay and made a note that Dartington issued them with a certificate and a velvet bag. (Therefore, someone with a certificated example may provide the answer you are looking for!)
I don't own one, but I do have an unsigned and un-numbered plaque depicting Mozart which is pictured on page 142 of the same book.
Hope that helps!
Chris.