Congratulations on your purchase. I recently bought one myself, but with three compensated valves: robust instruments with a dark, warm and focused sound, typical of the British Bessons of the 60s/70s of the last century. To obviate the annoying noise of the metal guides of the pistons I applied a thin layer of two-component epoxy resin to the sides: a problem easily solved in short time with negligible expense.
2007 Besson Prestige 2052, 3D+ K&G mouthpiece; JP373 baritone, 4B modified K&G mouthpiece; Bach 42GO trombone, T4C K&G mouthpiece; 1973 Besson New Standard 3 compensated valves, 3D+ K&G modified mouthpiece; Wessex French C tuba, 3D+ K&G modified mouthpiece.