Here are some ways to determine the JCo version of the JAR file and/or native library (.so on Linux OS).
SAP JCo Library 3.1.4
Jar File: sapjco3.jar
$ jar xvf sapjco3.jar
$ vim ./META-INF/MANIFEST.MF
Created-By: 8.1.048 10.0.2+000 (SAP AG)
Implementation-Title: com.sap.conn.jco
Implementation-Vendor-Id: com.sap
Implementation-Version: 20210330 1039 [3.1.4 (2021-03-30)]
Specification-Title: SAP Java Connector v3
Specification-Vendor: SAP SE, Walldorf
Specification-Version: 3.1.4
Native Library: libsapjco3.so
$ strings libsapjco3.so | grep "#\[%\]SAP" | sort
#[%]SAP
#[%]SAPCompatibilityLevel: 1
#[%]SAPFileVersion: 7530, 811, 31, 27526
#[%]SAPPlatform: linuxx86_64
#[%]SAPProductVersion: 753, patch 811, changelist 2059142
#[%]SAPSpecialBuild: optU (Mar 30 2021, 12:06:31)
SAP JCo Library 3.1.8
Jar File: sapjco3.jar
$ jar xvf sapjco3.jar
$ vim ./META-INF/MANIFEST.MF
Created-By: SAP SE, Walldorf
Implementation-Title: com.sap.conn.jco
Implementation-Vendor-Id: com.sap
Implementation-Version: 20230711 2000 [3.1.8 (2023-07-11)]
Specification-Title: SAP Java Connector v3
Specification-Vendor: SAP SE
Specification-Version: 3.1.8
Native Library: libsapjco3.so
$ strings libsapjco3.so | grep "#\[%\]SAP" | sort
#[%]SAP
#[%]SAPCompatibilityLevel: 1
#[%]SAPFileVersion: 7530, 1216, 33, 43451
#[%]SAPPlatform: linuxx86_64
#[%]SAPProductVersion: 753, patch 1216, changelist 2206139
#[%]SAPSpecialBuild: optU (Jul 11 2023, 19:49:38)
SAP JCo Library 3.1.9 (Released: March 28, 2024)
Jar File: sapjco3.jar
$ jar xvf sapjco3.jar
$ vim ./META-INF/MANIFEST.MF
Created-By: SAP SE, Walldorf
Implementation-Title: com.sap.conn.jco
Implementation-Vendor-Id: com.sap
Implementation-Vendor: SAP SE
Implementation-Version: 20240320 1328 [3.1.9 (2024-03-19)]
Specification-Title: SAP Java Connector v3
Specification-Vendor: SAP SE
Specification-Version: 3.1.9
Native Library: libsapjco3.so
$ strings libsapjco3.so | grep "#\[%\]SAP" | sort
#[%]SAP
#[%]SAPCompatibilityLevel: 1
#[%]SAPFileVersion: 7530, 1314, 34, 7755
#[%]SAPPlatform: linuxx86_64
#[%]SAPProductVersion: 753, patch 1314, changelist 2235979
#[%]SAPSpecialBuild: optU (Mar 20 2024, 13:17:44)
SAP JCo Library 3.1.10 (Released: June 21, 2024)
Jar File: sapjco3.jar
$ jar xvf sapjco3.jar
$ vim ./META-INF/MANIFEST.MF
Created-By: SAP SE, Walldorf
Implementation-Title: com.sap.conn.jco
Implementation-Vendor-Id: com.sap
Implementation-Vendor: SAP SE
Implementation-Version: 20240615 0037 [3.1.10 (2024-06-14)]
Specification-Title: SAP Java Connector v3
Specification-Vendor: SAP SE
Specification-Version: 3.1.10
Native Library: libsapjco3.so
$ strings libsapjco3.so | grep "#\[%\]SAP" | sort
#[%]SAP
#[%]SAPCompatibilityLevel: 1
#[%]SAPFileVersion: 7530, 1325, 34, 16950
#[%]SAPPlatform: linuxx86_64
#[%]SAPProductVersion: 753, patch 1325, changelist 2245174
#[%]SAPSpecialBuild: optU (Jun 15 2024, 00:25:56)