I was going to post much the same as Meg - Brian would probably be the best person to ask about this.
He has had computer problems recently which have kept him offline, but hopefully he will be able to answer your query.
All I know is that the figures with the 'Valetta' imprint are much harder to come by these days than the standard Maltese Grandmaster knight figures, so you would probably get a higher price for a specially marked one at auction, even if it isn't still bagged.
According to information long ago obtained from
Richard, the first grandmaster knight was released before 1998 and could be obtained through a donation to Valletta.