Here are a couple of tables to help you out. The accuracy isn't guaranteed, but it should be a good start.
Other Clarinets
Conn Clarinet Serial Number List
From Dave Surber of Leblanc:
Locate Henri Selmer Paris instrument serial numbers. Selmer (Paris) Sax Legend: Year: Model: Serial Number: 1922: Model 22: 750-1400: 1923. Unfortunately our serial numbering system and records were not set up for ease in locating this information. We currently manufacture or distribute several brands of wind instruments. Each one of these lines has numerous models of instruments and unfortunately in some cases each model has its own series of serial numbers.
Why Clarinets Crack; Wood Clarinet Oiling; Clarinet Bore Sizes; Embouchure; Theory; Nickel Silver; Prices. 1982 Prices and Models; Clarinet Values – How Much Is Mine Worth; Help Identifying My Clarinet; Saxophones. Saxophone Project – Help Needed; Saxophone Serial Numbers; Buescher Sax; Buffet Sax; Cleveland Sax; Conn Sax; King Sax; Martin. Over 100 company's databases containing dates of manufacture of musical instruments. Main index Clarinet, Flute, Piccolo, Oboe and Bassoon page Clarinet Model List The Clarinet Model List. This page contains a clarinet model number list. It includes models up to 1969. The choice of 1969 as an end date is due to the fact that Conn was bought by MacMillan in 1969/1970. New models after 1970 are therefore not included.
'Interested individuals may contact Leblanc's customer service department who will do their best to help them with as much information as we have available. However our records are only available from 1964 to the present.
We have limited records available to us and we do our best to provide as accurate information as we have. Unfortunately our serial numbering system and records were not set up for ease in locating this information.
We currently manufacture or distribute several brands of wind instruments. Each one of these lines has numerous models of instruments and unfortunately in some cases each model has its own series of serial numbers. These series of numbers have not been maintained in separate lists but are recorded together in our sales records that begin in 1964. It can take a considerable amount of time to locate a particular serial number if we do not have any idea of the model or when it was originally sold.
Individuals reselling used instruments should be responsible for supplying details of the original purchase ie: warranty registration documents or sales receipt information which would confirm the model and serial number of the instrument and the date it was originally purchased.
There is a Blue Book for Musical Instruments Published by Orion Research that is available to determine the value of many used instruments on the market today. Their web site is http://www.orionbluebook.com/
Conn Trombone Serial Number List
For appraisal of vintage instruments or historical information you may wish to contact the Shrine to Music Museum at The University of South Dakota in Vermillion. They may be able to provide you with a list of licensed qualified appraisers who specialize in different areas ie: strings, winds, keyboard, primitive etc..
We suggest you contact your local music dealer if you have further questions about purchasing or selling an instrument.
Thank You,
Leblanc Service Dept.'
If worst comes to worst you could try to contact the manufacturer. You can find contact information in the Retail section of these pages.