Thank you for contacting Mearto with your appraisal inquiry. Based on the photographs and information provided, this is a Martin Freres Paris Series, 1740 Model Bb Bass Clarinet in Grenadilla Wood, circa 1940s to 1960s. This Professional piece includes its original case with original paperwork, which adds a premium to the appraisal. The entire piece appears in very good to excellent condition. Based on prior sales and listings from vintage instrument resellers, and subject to play testing and examination for any condition issues not apparent in the photographs provided, its Fair Market Value is estimated at $1,000 to $1,500 USD.