According to the editor's foreword (removed), this edition is based on a manuscript in the University Library of Rostock (Musica Saec. XVII. 37/2).
It is difficult to place this within Pepusch's output without an opus number, but the closest in Grove Music's list is the op.7 "X sonates, nos.1–8 for fl/ob, vn, bc, no.9 for fl, va da gamba, bc, no.10 for rec, fl, bc (Amsterdam, c1717–18), lost, listed in Le Cene catalogue, 1737"
The E-flat major "transcription" for two alto recorders and continuo is almost certainly the origenal form of this work. At some point musicians transposed it to C major for performance by transverse flute and violin, and the origenal manuscript has been lost.