Yes Mur410,s.
Look rather large like they can take some amperage.
The board has led's on each mosfet (IRF540Z).
Led on 12v supply and led on 8v supply regulators.
Large MOV on DC battery supply.
3 pots per 556, PWwavelength, fine and coarse.
Didn't notice frequency??? maybe that's the fine and coarse adjusts.