Generally the Solace API version is contained in the name of the Solace jar. For example: sol-jcsmp-7.0.0.63.jar.
Internally within the Solace jar there will also be a manifest file in the META-INF directory which contains the version information. For example:
Manifest-Version: 1.0
Ant-Version: Apache Ant 1.8.2
Created-By: 1.7.0_17-b02 (Oracle Corporation)
Name: com/solacesystems/jcsmp
Specification-Title: Solace Systems Messaging API for Java
Specification-Version: 7.0.0.63
Specification-Vendor: Solace Systems, Inc.
Implementation-Title: com.solacesystems.jcsmp
Implementation-Version: 7.0.0.63
Implementation-Vendor: Solace Systems, Inc.
Additionally, it is also possible for applications to get the Solace API version programmatically as follows:
JCSMPRuntime.onlyInstance().getVersion().getSwVersion()
So it would sort of depend on how your applications was packaged which of these methods would be most appropriate.