Its a variac, so it doesn't provide any isolation. Wired to cover 0 to above 120V (boost) with a suitable miniature circuit breaker matching the transformer current rating (which can be a bit complex for variacs as their rating depends on the wiper position), it could be a very handy bit of kit if you are into small appliance repair or designing and developing mains input PSUs.
It appears to be fairly nicely put together, and having both voltage and current meters is an advantage, but if you are short of cash and haven't yet got a decent temperature controlled soldering iron, bench PSU, a decent DMM and a usable scope, unless its a very good bargain you may want to skip this one. N.B. Variac prices are heavily dependent on the current rating. Did you photo the terminal plate of the variac itsself, which probably had some data or a model number on it? If not, what was the max scale reading on the ammeter?