How to find Web Start version number?

How do you find a javaws version number? - have tried javaws -version to no avail, and had a trawl around but can't seem to find this - apologies if it's blindingly obvious

Reason for asking - trying to help out some guys here who support some legacy java apps and get some strange combinations of errors. Some of these may be due to the use of old admin scripts that re-install Web Start to a given path - so I suspect newer versions of jaws are being overwritten with older ones, or vice-versa on occasions. Would help to investigate this if could easily check the version of the javaws.exe in situ.