diff --git a/configure/CONFIG_BASE b/configure/CONFIG_BASE
index e416f99db..ab30d7f8b 100644
--- a/configure/CONFIG_BASE
+++ b/configure/CONFIG_BASE
@@ -14,8 +14,8 @@
 EPICS_BASE_HOST_BIN = $(EPICS_BASE)/bin/$(EPICS_HOST_ARCH)
 EPICS_BASE_HOST_LIB = $(EPICS_BASE)/lib/$(EPICS_HOST_ARCH)
 ifdef T_A
-EPICS_BASE_LIB      = $(EPICS_BASE)/lib/$(T_A)
-EPICS_BASE_BIN      = $(EPICS_BASE)/bin/$(T_A)
+  EPICS_BASE_LIB    = $(EPICS_BASE)/lib/$(T_A)
+  EPICS_BASE_BIN    = $(EPICS_BASE)/bin/$(T_A)
 endif
 
 #---------------------------------------------------------------
@@ -33,8 +33,10 @@ EPICS_BASE_HOST_LIBS += ca Com
 # Version number for base shared libraries (and win32 products)
 
 ifdef BASE_TOP
-SHRLIB_VERSION = $(EPICS_VERSION).$(EPICS_REVISION)
-PROD_VERSION = $(EPICS_VERSION).$(EPICS_REVISION)
+  # Unix lib.so.<v.r.m>  Darwin lib.<v.r.m>.dylib
+  SHRLIB_VERSION = $(EPICS_VERSION).$(EPICS_REVISION).$(EPICS_MODIFICATION)
+  # Windows only allows 2 levels of version numbering
+  PROD_VERSION = $(EPICS_VERSION).$(EPICS_REVISION)
 endif # BASE_TOP
 
 #---------------------------------------------------------------
@@ -84,12 +86,15 @@ ELEX = $(call PATH_FILTER, $(TOOLS)/e_flex$(HOSTEXE)) -S$(EPICS_BASE)/include/fl
 YACC  = $(EYACC)
 LEX   = $(ELEX)
 
+#---------------------------------------------------------------
+# msi used to be an external tool
+
+MSI  ?= $(EPICS_BASE_HOST_BIN)/msi
+
 #---------------------------------------------------------------
 # External tools and tool flags - must be in path or defined in application
 
-ifndef ADL2DL
-ADL2DL = adl2dl
-endif
+ADL2DL ?= adl2dl
 
 # sch2edif compiler and flags
 SCH2EDIF = sch2edif
@@ -99,18 +104,11 @@ SCH2EDIF_FLAGS =
  
 # e2db and flags
 #    - again there is an assumption where edb.def is installed.
-ifndef E2DB
-E2DB = e2db
-endif
+E2DB ?= e2db
 E2DB_SYSFLAGS = -ate -d $(CAPFAST_TEMPLATES)/edb.def
 E2DB_FLAGS =
 
-ifndef DBST
-DBST = dbst
-endif
-
-ifndef MSI
-MSI = $(EPICS_BASE_HOST_BIN)/msi
-endif
+DBST ?= dbst
+
 
 
diff --git a/configure/os/CONFIG.darwinCommon.darwinCommon b/configure/os/CONFIG.darwinCommon.darwinCommon
index c3f6eddf9..fc760c0f2 100644
--- a/configure/os/CONFIG.darwinCommon.darwinCommon
+++ b/configure/os/CONFIG.darwinCommon.darwinCommon
@@ -68,13 +68,12 @@ GNU = NO
 #
 # Darwin shared libraries
 #
-SHRLIB_VERSION = $(EPICS_VERSION).$(EPICS_REVISION).$(EPICS_MODIFICATION)
 SHRLIB_LDFLAGS = -dynamiclib -flat_namespace -undefined suppress \
-       -install_name $(shell $(FULLPATHNAME) $(INSTALL_LIB))/$@ \
-       -compatibility_version $(EPICS_VERSION).$(EPICS_REVISION) \
-       -current_version $(SHRLIB_VERSION)
+    -install_name $(shell $(FULLPATHNAME) $(INSTALL_LIB))/$@ \
+    $(addprefix -compatibility_version , $(SHRLIB_VERSION)) \
+    $(addprefix -current_version , $(SHRLIB_VERSION))
 SHRLIB_SUFFIX_BASE = .dylib
-SHRLIB_SUFFIX = .$(SHRLIB_VERSION)$(SHRLIB_SUFFIX_BASE)
+SHRLIB_SUFFIX = $(addprefix ., $(SHRLIB_VERSION))$(SHRLIB_SUFFIX_BASE)
 
 LOADABLE_SHRLIB_LDFLAGS = -bundle -flat_namespace -undefined suppress
 
diff --git a/configure/os/CONFIG.win32-x86.win32-x86 b/configure/os/CONFIG.win32-x86.win32-x86
index 0ffcd2606..0ac715d6f 100644
--- a/configure/os/CONFIG.win32-x86.win32-x86
+++ b/configure/os/CONFIG.win32-x86.win32-x86
@@ -130,6 +130,7 @@ RANLIB=
 # -LTCG whole program optimization
 # -incremental:no full linking
 # -fixed:no generate relocatable code
+# -version:<major>.<minor> - only 2 components allowed, 0-65535 each
 # -debug generate debugging info
 LINK_OPT_FLAGS_YES = -LTCG -incremental:no -opt:ref \
     -release $(PROD_VERSION:%=-version:%)
diff --git a/documentation/RELEASE_NOTES.html b/documentation/RELEASE_NOTES.html
index 207cd2d93..dc76e2b86 100644
--- a/documentation/RELEASE_NOTES.html
+++ b/documentation/RELEASE_NOTES.html
@@ -14,6 +14,15 @@
 <h2 align="center">Changes between 3.15.0.2 and 3.15.1</h2>
 <!-- Insert new items immediately below here ... -->
 
+<h3>Shared Library Versions</h3>
+
+<p>On architectures that can support it, the shared library version number for
+libraries provided with Base has had the third component of the EPICS version
+number added to it, thus libCom.so.3.15.1 instead of libCom.so.3.15. Windows
+can only support two components to its internal product version number, and the
+Darwin bug that external shared libraries were being built using the EPICS
+version number has been fixed.</p>
+
 <h3>Hooking into dbLoadRecords</h3>
 
 <p>A function pointer hook has been added to the dbLoadRecords() routine, to