I'm building from the source zip and jaxb-impl.jar is in different locations but doesn't have the same md5sums:
dbe5131e4e2663a4b8832ce44f8af453 src/build/output/jboss-as/client/jaxb-impl.jar
889c73f7436786f8e4e7aeae255b6c11 src/build/output/jboss-as/server/all/deploy/jbossws.sar/jaxb-impl.jar
889c73f7436786f8e4e7aeae255b6c11 src/build/output/jboss-as/server/production/deploy/jbossws.sar/jaxb-impl.jar
889c73f7436786f8e4e7aeae255b6c11 src/build/output/jboss-as/server/default/deploy/jbossws.sar/jaxb-impl.jar

the jar in the client dir has following MANIFEST:
Manifest-Version: 1.0
.
Build-Id: 05/26/2009 06:25 PM(mockbuild)
.
Implementation-Version: 2.1.4-05/26/2009 06:25 PM(mockbuild)-fcs

the jars in the server dirs have following MANIFEST:
Manifest-Version: 1.0
.
Build-Id: 05/06/2009 04:43 PM(mockbuild)
.
Implementation-Version: 2.1.4-05/06/2009 04:43 PM(mockbuild)-fcs

++++++++++++++++++++++++++++++++++++++++++++++++++++++++

jaxb-xjc.jar differs when building from src zip and svn:
MANIFEST in src zip:
...
Build-Id: 05/26/2009 06:25 PM(mockbuild)

MANIFEST in svn:
...
Build-Id: 05/05/2009 08:05 PM(mockbuild)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++

jaxws-rt.jar differs when building from src zip and svn:

MANIFEST in src zip:
...
Created-By: 1.5.0_18-b02 (Sun Microsystems Inc.)
Build-Id: 05/25/2009 08:11 PM(mockbuild)
Build-Version: JAX-WS RI 2.1.1-05/25/2009 08:11 PM(mockbuild)-

MANIFEST in svn:
...
Created-By: R27.1.0-109-73164-1.5.0_08-20061129-1418-linux-ia32 (BEA Systems, Inc.)
Build-Id: 07/21/2008 10:18 AM(brewbuilder)
Build-Version: JAX-WS RI 2.1.1-07/21/2008 10:18 AM(brewbuilder)-