Is it safe to assume that the marks would have started with "A"? If we go off of that assumption (and assumptions can be dangerous) and if Pieter's "DE" was awarded in 1983, could the start then have been in 1980? If this is true, then we should see upwards of "W", (possibly "X" if any old style medals were ever made in 2003), but no "Y" or "Z"" as the first character. Do we know this to be the case?
As for the 2nd "digit" - if that represents a month, we should see A thru L. This makes sense, but do we know this to be the case? Also, we introduce an issue with this theory - in 2003, the letters appear to recycle back to "A" - but then we see the use of a number as the second mark - but our problem is that we only have 0 thru 9! We'd be missing two months in this scheme.
What do you think gents?