A full bridge of four IRF840 MOSFETs. Each half is driven through its own isolation transformer from an MC33152 gate driver, so it is a properly isolated full bridge rather than a simple totem pole. The KiCad schematic is titled "DRSSTC HV Primary-Side" and dated March 2021. The separate hand-soldered control board in the photo carries the oscillator and variable-PWM logic that feeds the two MC33152s. The unusual part is the mechanics. The whole structure (coil mounts, base feet, connector clips, topload assembly) is modelled in OpenSCAD and 3D-printed instead of built from tube and wood. The repository and schematic both say "DRSSTC," but the author's own notes correct that: "this coil is singly-resonant, not doubly-resonant," so in practice it is an SSTC.
Schematics and photos
schematic (AgentElement, DRSSTC HV Primary-Side, Mar 2021)
Sources
This is the card from the driver tree, written from what the builder published. Send corrections through the forum.