The old Frisian incunabulum known as 'Druk' (1485) contains a conversion directive concerning the way in which amounts in the old Frisian compensation registers, quoted in antiquated (11th to 14th century) money, should be converted into current (15th century) money.
It is analysed in the author's thesis on the evolution of the money standard in medieval Frisia (c.600-c.1500), which has recently been published. However, so far, this analysis did not take into account a handwritten gloss also regarding the conversion of compensation amounts, found in a particular copy of this incunabulum which has been in the possession of the secretary of the town of Leeuwarden, Hemma Odda zin (in around 1500). Besides a confirmation of what was already found in the thesis, the analysis of this gloss generated some new view-points. Among others a new possible answer is found to the question as to why in the directive a grata (old Vleemse grote) was valued at 2 old English pennies, whereas its real value was about 1 old English penny as appears from other sources of the time.
The new answer is that this valuation might be a trick, not only to the purpose of converting compensation amounts in old English money into grate but at the same time of halving these amounts to put back their doubling during the 13th century which was made in a vain effort to ensure a Peace of God among the Frisians.