A Franco-Flemish double-manual harpsichord,
Details about the Ioannes Ruckers rosette in the Franco-Flemish harpsichord
The rosette in the instrument is slightly too small for the hole into which it has been placed. The original soundboard rosette, which was clearly larger, must have been removed, probably in the eighteenth century, and replaced with a genuine “HR” rosette. The replacement rosette is of the type used by Ioannes Ruckers after his father's death in 1598 and until his royal court appointment in 1614. It is very similar to that which is shown in Figure 7.24, page 160 of my book.
The original border of the inside of the hole in the soundboard (81mm) can be seen clearly in places. This is considerably greater than the diameter of the normal Ioannes Ruckers rosette from the period 1598-1614, which has a diameter of 65mm. Because this rosette has the correct diameter and is otherwise an identical casting to the rosettes in numerous genuine Ioannes Ruckers instruments, it appears to be a genuine early Ioannes Ruckers rosette. The gap between the edge of the rosette and the inside of the bevel in the soundboard wood has been filled out with gesso or some other filler.
There are also signs underneath the soundboard of the former existence of a slightly larger soundboard rosette which must have been glued into the instrument sometime before the present one. The present rosette is also not taped to the lower surface of the soundboard with the characteristic four pieces of linen cloth normally used by the members of the Ruckers/Couchet family to hold the rosette in position. Instead the rosette is held here by a single piece of linen cut into a circle and glued all round the rosette. There can therefore be no doubt about this rosette: it is an original Ioannes Ruckers rosette, but is clearly not original to this instrument.
 Grant O’Brien, Ruckers. A Harpsichord and Virginal Building Tradition, (Cambridge University Press, Cambridge, 1990; digital reprint, Cambridge: Cambridge University press, 2008).