Using geoserver I have some layers in CRS EPSG: 20935 (Arc 1950 UTM 35S). In order for them to work with base map layers (in leaflet) I set the native projection to 20395, the declared projection to 4326 (WGS 84) and ask geoserver to reproject to declared. This works and I can see my layers on leaflet map. The base maps are in web mercator but as I understand it 4326 will work.
However, using ArcGIS doing the same reprojection there are ~9 options as to which transformation to use. Given the location of my data number 7 would be most appropriate. Testing ArcGIS's "layer to kml" tool I discovered that ArcGIS defaults to reproject using the first transformation (ARc1950 to WGS84(1)) which leads to an East West shift of 30 - 70 metres compared to transformation(7). So in Arc it is necessary to reproject to WGS84 first (selecting the desired transformation). How can I find out what transformation geoserver is using?