[5] The lack of census records showing the Rugeri name may be explained by the possibility of Francesco not being an indoor apprentice, but one who lived and boarded at his own home while apprenticing.
Hill & Sons note that the "unmistakable" handiwork of Francesco Rugeri can be found, in certain of Nicolo Amati's works, and just like Antonio Stradivari and Andrea Guarneri, Francesco from time to time included the words "Alumnus Nicolai Amati" on his labels, further adding to the evidence of his apprenticeship.
[9] For example, there exists a violin labelled "Francescus Rugerius Alumnus Nicolai Amati fecit Cremonæ 1663".
[13] A court case was brought in 1685 by a violinist seeking relief from the Duke of Modena as a victim of fraud.
[14] However, this case may also indicate that Rugeri, who was working in the shadow of the great Cremona makers—Amati, Guarneri, and Stradivari—had resorted to a desperate act to make a sale.
Some researchers believe there is a closer educational association between Antonio Stradivari and Francesco Rugeri than has previously been recognized.
Some researchers believe early instruments by Stradivari bear a stronger resemblance to Francesco Rugeri's work than Amati's.
This pin or hole was fundamental in the graduation of the thickness of the plates, and was obviously a technique passed on through generations of pupils of the Amati.
[22] Cellos made by other luthiers of the period are often quite massive and fairly unmanageable for modern players' usage unless severely cut down in size.
[24] Interestingly, Francesco had two sons he named Giacinto—the first was born in 1658 and baptized Nov 19th 1658 with Nicolò Amati being the Godfather.