Is a 1948 mint condition Selmer France Model K clarinet worth a lot I also have the original case mint condition?

Answer 1

When you say Model K, do you mean that the serial number starts with K?  These are usually called K Series.  They date to the late 1920's or early 1930's.

A Selmer Paris K Series clarinet in genuine mint condition does have some value.  Depending on the keywork and whether it is early or late in the series (this was a time of rapid innovation at Selmer), they're worth $500 - $2000, more likely in the lower part of that range.  The most valuable are what are sometimes referred to as a three-in-a-row Improved Albert.

Answer 2

I think it's quite valuable. Can you identify if it's Boehm or Albert System? If it has 4 rings on the upper part and not 5 or six then it's definitely Albert system.