Transformer and MOSFET combination not working
It appears to be a high voltage controlled power tool used as an engraver. These often have diamond tips.



There is a current limiter of 2.1A on 24Vdc and a FET complementary drive to a centre-tapped boost transformer.  Thus it draws less than 50W.

PWM control is a guess, although it could be frequency control for resonance.
Piezo is just a guess too.

The electronics are similar to a high-frequency AC Boost transformer with AC coupled output.  That suggests to me it is a Piezo load.