After the invention of the valves at the beginning of the 19th century, an exciting transition period arose, during which various trumpet concepts were formed. The natural trumpets of the classical period had their continued existence and existed parallel to the new valve instruments.
A special contemporary witness to this development are the invention trumpets and piston trumpets after Courtois. Although the piston trumpet could be played entirely chromatically in principle, it was equipped with crooks. So it could be played from G to Bb downwards in 7 keys. The same crooks were played on the valveless invention trumpet. Depending on the situation, there were frequent back and forths between the two.
This went so far that both instruments had a common double case as a set, with which one could go to rehearsals and performances and always had both at hand.