That doesn't look like a serial number. I'm not an expert on clarinets, but I think in this case the 424N is the model number and the serial number proper is the part starting with B, which according to Conn's website
http://www.conn-selmer.com/en-us/about/customer-service/serial-numbers/conn/
puts it in the early 1960s.
To get an estimate of the value you'd need to take it to a dealer.
Your Conn clarinet plays in the key of C and was made in 1925.
To determine the value of a Conn clarinet with the serial number C85400, one must consider factors such as its condition, model, age, and market demand. Typically, models from Conn can range in value from a few hundred to over a thousand dollars. It's advisable to consult recent sales data, check with musical instrument appraisers, or visit online marketplaces for a more accurate valuation.
Early 1920.
1960
eighty years old
It is potentially a 1928 model. I found this page on the serial numbers related to the year of the clarinet. The link is located in the related links section below.
Artie Shaw played a Conn clarinet. His clarinet is now in the Smithsonian storage facility. Unfortunately, Conn is no longer an independent entity. It was acquired by Selmer, another company most commonly associated with Benny Goodman.
1935. The "E" indicates that it is an alto in Eb, and the "L" indicates that it is pitched at a1=440 hz. Source:http://www.woodwind.org/clarinet/Equipment/HowOld/BBBC.html
what is face value for saturdays ticket between msu and u conn
$125.000
500-800 dollars
100-300