Add properties to proserver sources document
in your configuration eg proserver.ini add a properties line with -> seperated key value pairs each sep by ; [cath_pdb] title = CATH Domains ... properties = spec -> DAS/1.6E ; label -> eFamily
In this case the spec option tells the DAS registry that this data source is a 1.6 version. This can be used on a per source basis.
Note: you can also situate your proserver.ini file and call it something else by starting proserver with the -c option and specifying where the config file you want to run is.