This basic instrument (a Maggini copy) is made by Calvert Violins in Baltimore, MD, USA for Rickert & Ringholz Musical Instruments in Atlanta, GA, USA. The baritone (octave) conversion is done by Rickert & Ringholz.
The conversion was inspired by a customer and designed (if you want to call it design) by Don Rickert. Conversion involves re-cutting the nut and bridge, installing Super-Sensitive Sensicore Octave Strings (Thomastik octave strings sound horrible on this instrument, but they do sound OK on lesser instruments), adjusting the soundpost and installing a Wittner polycarbonate tailpeice (the tailpeice is not shown in the photos). As soon as they are available in the U.S. Wittner planetary geared tuning pegs will be part of the conversion...the photos show very nicely fit rosewood pegs.
While this instrument can be played relatively effectively with a very high quality violin bow, Don Rickert recommends only a Glasser Octagonal braided carbon fiber viola bow or the new CodaBow Diamond Series braided carbon fiber viola bow for this instrument to achieve its full potential.
Note: While a 14" viola is a better base instrument than a regular violin for an octave conversion, this Maggini replica is actually larger (more air space) than a 14" viola and has a far superior sound and better playability.