Carolus Hellmer (Karel Boromejský Ondřej Hellmer, 1739–1811) was one of the key figures of the Prague violin-making school in the 18th century. The Hellmer family belonged to a distinguished lineage of violin makers. Born in Smíchov, then a small settlement outside Prague, Carolus studied under his father, Johann Georg Hellmer, as well as Johann Ulrich Eberle, who had already established a successful workshop in Prague. Hellmer later traveled to Germany to apprentice with several luthiers, although historical records neither specify the duration of his stay nor identify the masters under whom he trained. He returned to the present-day Czech Republic around 1763 and was granted Prague citizenship in the Malá Strana district. Hellmer continued to live and work in Prague, passing down his family’s violin-making tradition to one of his seven sons, Karl Boromeus Andreas Hellmer.

Carolus Hellmer’s instruments closely resemble those of Eberle, reflecting influences from both Jacob Stainer and the Cremonese tradition. They feature a flatter arching than Stainer’s models, resulting in greater projection, while retaining softer, more rounded edges than those typically found on Cremonese instruments. This particular violin is especially characteristic of Hellmer’s work in its scroll, which is deeply undercut and features a pronounced eye.

Perhaps the most distinctive feature of this instrument is the presence of small circular carvings on the back plate, commonly referred to by Czech luthiers as švestková povidla (“plum jam”). These plum-like carvings can be seen on the treble side of the back plate. Hellmer’s varnish is generally darker than Eberle’s, displaying a rich orange-brown hue that has naturally matured over time into a deeper brown with subtle orange highlights.

Tonally, the instrument possesses a beautifully resonant lower register combined with exceptional projection and brilliance in the upper register. It was restored by the younger Ladislav F. Prokop in 1977 and, more recently, by Jan Veselý.