I thoughed the roman numerals only allowed 3 of the same figures in a row? That is how i learned it in 4th grade (when i was 10 years old, so i might be mistaken).
So the 1417 date should read MCDXVII?
Either way, an impressive find.. though i like the munich barrel better.
edit: i read on wikipedia (not always a reliable source) that the notation of roman numerals varried greatly. The use of 4 or more of the same number is apparantly allowed.