It's an emission tester so it doesn't really tell you how the tube is performing as well as a mutual transconductance tester like a TV-7. Without knowing what "needs restoring" means and not knowing the asking price it is hard to say if it is worth it. Back in the 90s when one could pick up really pro testers for $150 and emission testers for $25 it was no big deal to have a few around.
But at current prices I don't think a tube tester is worth buying unless you buy and sell a lot of different tubes. If you have a couple of pieces of tube gear you can get a good idea of what shape the tubes it uses are in by measuring the voltages in the gear. And if you do buy and sell a lot of tubes it's best to be able to give a transconductance measurement with the tube. I've had a 707, TV-2, 539B, TV-10 D/U, a big old Mercury in-store emission tester and a few others over the years. I've also calibrated a Cardamatic (about 100 steps!). The only one I've kept (and which is used constantly) is the TV-10, which happens the be the first one I bought about 30 years ago.
