I just added the middle image to the below caption; you can find the caption and images in the Trombone History Timeline (1826-1850). The three prints are very similar. Yes, I know the Distin quintet later moved away from using trombone, but at one point they used a slide trombone.
c. 1834—England: Three very similar prints depicting the Distin Family Brass Quintet, an ensemble known for adopting Adolph Sax’s valve instruments, include a member holding a slide trombone, indicating the instrument was probably used at least during the early days of the ensemble (see below 3 images; public domain) (top image, by John William Gear: New York Public Library; bottom image: Baines, Brass plate XI). According to Dudgeon, “The early quintet performances of the Distin family used various combinations of keyed bugle, cornopean, slide trumpet, natural horns, and trombone; all made by the firm of Pace. By 1844, the Distins met Adolph Sax and made the switch to valved saxhorns” (Dudgeon, Keyed Bugle 28).