I perform on three boxes, a Saltarelle Irish Bouebe in D/G and Rowbotham-modified Hohner “Super-Preciosa” in D/Em and Hohner “Impiliput” in B/C.
The Bouebe is a 23 treble, 8 bass, two voice D/G melodeon with a flat keyboard and bass stop to take out the thirds. It has fourth button start with low notes and accidentals, with the standard layout. The accidentals have not been reversed. This instrument is standard and unmodified, and is serviced and tuned by Martyn White. I got this instrument second hand around 7 years ago from the Music Room at their stall at Sidmouth, to replace my original instrument, a very battered Delicia Popular.
The Preciosa is a project that was completed in 2011 by Mike Rowbotham. The treble end is a Hohner Preciosa (1935-1943), which is one of the smallest working two voice two row melodeons ever made. It has 21 treble buttons, plus four on the half row. The reeds are flat mounted onto the fondo, with a “flying” reedpan for the second voice. The treble is in D/Em, to a layout invented by myself. The bass end is a Hohner Regina (1937, 1940), which was orignally a piano accordion, albeit one so small as to be almost unusable. It has been fitted with a variant on the standard melodeon layout, such that the 12 basses are fully chromatic in bass, lacking only the G# and D# chords. All chords are thirdless. I have written in more detail about this instrument here.
The Impiliput is another Rowbotham creation, dating from 2012. It is a Hohner Liliput, but with the bass action and blocks from a Hohner Imperial I Piano Accordion spliced in. The tuning is B/C with the half row tuned to C# (F to F) and the bass end tuned to 12 unisonoric Hayden-style free bass, no chords. This enables the user to play complicated bass runs that aren’t possible on the other instruments. I wrote in more detail about this instrument here.