It's missing the glass.
Doesn't seem to be missing it to me.
Honestly you couldn't pick much of a worse machine to start with than a fully working Defender cocktail. In addition to basically destroying a working classic table you would also just be throwing money out the window as well by picking such an expensive donor machine when one could be had for so much less.
If hell bent on using that machine I would suggest the jrok multiwilliams PCB, it has Defender, Stargate, Robotron, Joust, Bubbles, Splat, Sinistar and Blaster all on one reproduction circuit board. I am running one in an upright Robotron cabinet myself.