diff --git a/VERSION b/VERSION
index 8f5a39a04..a69af5778 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.39.2
+2.39.3
diff --git a/definitions/grib2/local/ecmf/section4_extras.def b/definitions/grib2/local/ecmf/section4_extras.def
index 685ae5dc2..e19686298 100644
--- a/definitions/grib2/local/ecmf/section4_extras.def
+++ b/definitions/grib2/local/ecmf/section4_extras.def
@@ -4,7 +4,7 @@
 # This is only read when centre=ecmf, so can remove if statement that was here
 # This is ecmf local so we shouldnt use MasterDir. Instead we look for pseudocentre (conceptsDir2) then centre (conceptsLocalDirAll)
 
-concept modelName(unknown, "modelNameConcept.def", conceptsDir2, conceptsLocalDirAll): no_copy, dump, read_only;
+concept modelName(unknown, "modelNameConcept.def", conceptsDir2, conceptsLocalDirAll): no_copy, dump;
 
 if (modelName isnot "unknown") {
    concept modelVersion(unknown, "modelVersionConcept.[modelName].def", conceptsDir2, conceptsLocalDirAll): no_copy, dump, read_only;
diff --git a/definitions/grib2/localConcepts/ecmf/modelNameConcept.def b/definitions/grib2/localConcepts/ecmf/modelNameConcept.def
index bda170b5e..50215da26 100644
--- a/definitions/grib2/localConcepts/ecmf/modelNameConcept.def
+++ b/definitions/grib2/localConcepts/ecmf/modelNameConcept.def
@@ -1,12 +1,18 @@
 'IFS' = {
     backgroundProcess = 255;
 }
-'aifs-single-mse' = {
+'aifs-single' = {
     backgroundProcess = 1;
 }
-'aifs-ens-crps' = {
+'aifs-ens' = {
     backgroundProcess = 2;
 }
-'aifs-ens-diff' = {
+'aifs-single-mse' = {
     backgroundProcess = 3;
 }
+'aifs-ens-crps' = {
+    backgroundProcess = 4;
+}
+'aifs-ens-diff' = {
+    backgroundProcess = 5;
+}
diff --git a/definitions/grib2/localConcepts/ecmf/modelVersionConcept.aifs-ens-crps.def b/definitions/grib2/localConcepts/ecmf/modelVersionConcept.aifs-ens-crps.def
index b06e75f21..8c6d63d00 100644
--- a/definitions/grib2/localConcepts/ecmf/modelVersionConcept.aifs-ens-crps.def
+++ b/definitions/grib2/localConcepts/ecmf/modelVersionConcept.aifs-ens-crps.def
@@ -1,2 +1 @@
-'v1' = { generatingProcessIdentifier = 1; }
-'v2' = { generatingProcessIdentifier = 2; } 
+'v0.1' = { generatingProcessIdentifier = 1; }
diff --git a/definitions/grib2/localConcepts/ecmf/modelVersionConcept.aifs-ens.def b/definitions/grib2/localConcepts/ecmf/modelVersionConcept.aifs-ens.def
new file mode 100644
index 000000000..59a485298
--- /dev/null
+++ b/definitions/grib2/localConcepts/ecmf/modelVersionConcept.aifs-ens.def
@@ -0,0 +1 @@
+'aifs-ens-crps-v0.1' = { generatingProcessIdentifier = 1; }
diff --git a/definitions/grib2/localConcepts/ecmf/modelVersionConcept.aifs-single-mse.def b/definitions/grib2/localConcepts/ecmf/modelVersionConcept.aifs-single-mse.def
index b06e75f21..ebad108bf 100644
--- a/definitions/grib2/localConcepts/ecmf/modelVersionConcept.aifs-single-mse.def
+++ b/definitions/grib2/localConcepts/ecmf/modelVersionConcept.aifs-single-mse.def
@@ -1,2 +1,3 @@
-'v1' = { generatingProcessIdentifier = 1; }
-'v2' = { generatingProcessIdentifier = 2; } 
+'v0.2.0' = { generatingProcessIdentifier = 1; }
+'v0.2.1' = { generatingProcessIdentifier = 2; }
+'v1.0' = { generatingProcessIdentifier = 3; }
diff --git a/definitions/grib2/localConcepts/ecmf/modelVersionConcept.aifs-single.def b/definitions/grib2/localConcepts/ecmf/modelVersionConcept.aifs-single.def
new file mode 100644
index 000000000..b636f15c9
--- /dev/null
+++ b/definitions/grib2/localConcepts/ecmf/modelVersionConcept.aifs-single.def
@@ -0,0 +1,3 @@
+'aifs-single-mse-v0.2.0' = { generatingProcessIdentifier = 1; }
+'aifs-single-mse-v0.2.1' = { generatingProcessIdentifier = 2; }
+'aifs-single-mse-v1.0' = { generatingProcessIdentifier = 3; }
diff --git a/tests/grib_modelName.sh b/tests/grib_modelName.sh
index cbc0a4501..5a9dc5d1b 100755
--- a/tests/grib_modelName.sh
+++ b/tests/grib_modelName.sh
@@ -23,12 +23,13 @@ tempRef=temp.$label.ref
 sample=$ECCODES_SAMPLES_PATH/GRIB2.tmpl
 
 ${tools_dir}/grib_set -s generatingProcessIdentifier=1,backgroundProcess=1 $sample $tempGrib
-grib_check_key_equals $tempGrib modelName,modelVersion "aifs-single-mse v1"
+grib_check_key_equals $tempGrib modelName,modelVersion "aifs-single aifs-single-mse-v0.2.0"
 
-${tools_dir}/grib_set -s generatingProcessIdentifier=154 $sample $tempGrib
+# IFS is backgrounbdProcess=255 to preserve backward compatibility§
+${tools_dir}/grib_set -s generatingProcessIdentifier=154,backgroundProcess=255 $sample $tempGrib
 grib_check_key_equals $tempGrib modelName,modelVersion "IFS cy48r1"
 
-${tools_dir}/grib_set -s generatingProcessIdentifier=100 $sample $tempGrib
+${tools_dir}/grib_set -s generatingProcessIdentifier=100,backgroundProcess=255 $sample $tempGrib
 grib_check_key_equals $tempGrib modelName,modelVersion "IFS unknown"
 
 # Check that this only works for centre ecmf
@@ -40,27 +41,24 @@ ${tools_dir}/grib_set -s generatingProcessIdentifier=1,backgroundProcess=1,centr
 ${tools_dir}/grib_set -s generatingProcessIdentifier=1,backgroundProcess=3,productionStatusOfProcessedData=13 $sample $tempGrib
 grib_check_key_equals $tempGrib modelName,modelVersion "ALARO cy46h1"
 ${tools_dir}/grib_set -s productionStatusOfProcessedData=0 $tempGrib $temp2Grib
-[ $( ${tools_dir}/grib_get -f -p modelName $temp2Grib ) = "aifs-ens-diff" ]
-[ $( ${tools_dir}/grib_get -f -p modelVersion $temp2Grib ) = "v1" ]
+grib_check_key_equals  $temp2Grib modelName    'aifs-single-mse'
+grib_check_key_equals  $temp2Grib modelVersion 'v0.2.0'
 
 
 # ECC-2010
 ${tools_dir}/grib_set -s marsClass=ai,typeOfProcessedData=missing,backgroundProcess=1,generatingProcessIdentifier=1 \
     $ECCODES_SAMPLES_PATH/reduced_gg_pl_32_grib2.tmpl $temp2Grib
-grib_check_key_equals $temp2Grib mars.model 'aifs-single-mse'
+grib_check_key_equals $temp2Grib mars.model 'aifs-single'
 
 ${tools_dir}/grib_set -s marsClass=ai,typeOfProcessedData=missing,backgroundProcess=2,generatingProcessIdentifier=1 \
     $ECCODES_SAMPLES_PATH/reduced_gg_pl_32_grib2.tmpl $temp2Grib
-grib_check_key_equals $temp2Grib mars.model 'aifs-ens-crps'
+grib_check_key_equals $temp2Grib mars.model 'aifs-ens'
 
 
-# Keys are read-only (may change this later)
-set +e
-${tools_dir}/grib_set -s modelName=AIFS $sample $tempGrib 2>$tempLog
-status=$?
-set -e
-[ $status -ne 0 ]
-grep -q "Value is read only" $tempLog
+# modelName not read-only
+${tools_dir}/grib_set -s class=ai,type=pf,stream=enfo,modelName='aifs-ens-crps' $ECCODES_SAMPLES_PATH/reduced_gg_pl_32_grib2.tmpl $tempGrib
+grib_check_key_equals $tempGrib mars.model 'aifs-ens-crps'
+grib_check_key_equals $tempGrib backgroundGeneratingProcessIdentifier 4
 
 set +e
 ${tools_dir}/grib_set -s modelVersion=cy48r1 $sample $tempGrib 2>$tempLog