The problem here is that Ruskin is trying to represent an inscription he did not understand at this stage. Ruskin came to see the word correctly as ‘quinque’ at Notebook M p.131. His guess here at that date was 1304 or 1314 shows clearly that he did not understand the inscription at this stage. The date is 1354, and that requires ‘mille trecentos’ for one thousand three hundred; ‘quatuor’ for four; ‘decies iam quinque’ i.e. five groups of ten, and so fifty, and that is what he came to see as the correct reading of the inscription. Zanotto and Selvatico had the date right; it seems to follow that Ruskin did not consult them when writing this.
[Version 0.05: May 2008]