70w Thorn "not-sodium" SON-T

I was given this NOS Thorn 70w SON-T lamp and it looks like it has never been used.
When I tested it however, it appears to be defective as when the lamp is started on normal 70w SON gear, the lamp current sits on about 1.15 amps and the lamp voltage does not want to rise above 17v.

I've tried it on 400w SON gear and while the lamp current is a lot higher, the lamp voltage still refused to rise.
I even tried it on my high-voltage 1000w metal halide gear and even then, the lamp voltage only rose to 19v and it was puling about 7 amps from the ballast!

It's worth noting that when it's being forced on the higher lamp current, the colour is very white.

It does seem that there is in fact, no sodium at all in this lamp!