1Kw Venture SON-T

Just got a load of these out of the lamp bin at work, no idea where they've come from as I don't think there's any 1kw SONs in use anywhere here.

As you can see they're used, however the couple I've tested so far seem to work fine including this one which appears to have an issue in that the black ring at the bottom of the jacket has gone? It appears to work fine but doesn't seem to quite reach full output, only showing about 950 watts on the power meter at full brightness.