Valves in brass instruments came into common use in early to mid 1800s,  but achieving perfect intonation while using a combination of valves was always a compromise- with some fundamentals or their partials being always slightly sharp or flat. Compensating valve systems developed in the late 1800s came closer to the objective of perfect intonation, but there were still anomalies that were not easily resolved.   One early solution -  tried in 1863 by Adolphe Sax, was a trombone with 6 independent valves- each with tuned lengths of tubing.  Another version in 1868, also by Sax, had 6 valves  and 7 independent bells! (scroll down for pics of the Sax Trombones)

This trombone, made by Josph Persy of Bruxelles,  uses 6 independednt Perinet style valves and 6 independent tuned lengths of tubing to achive fundamental notes and partials equivalent to those achieved by the 7 positions on a slide trombone - eg:  0, 1, 2, 3, 4, 5, 6, for a total of 7 positions, with 0 = 1st position(open),  1 = 2nd position, and so on.  The valves are operated by both hands - with the mouthpipe leading to the main tuning-slide, then in turn to valves for R1, R2, R3, L1, L2, L3. The bell pipe leads from valve for R1. A finger ring is provided for R4, and an adjustable finger rest for L4.

These trombones were used to some extent in France, but more often in Belgium. The great British conductor, Sir Henry Wood, liked them so much in 1919 he ordered a set for the Queen's Hall Orchestra. Apparently a set was used for the premiere of Elgar's 2nd Symphony.