Is that what I think it is? And if so, where did you get them?
These are complete plates. You can buy <80% complete plates with "drill here" schematics for about $400.00. Sten gun "blank" tubes with drawings are <$100.00.
Try subguns.com forum or Karma metal Co.
Remember to obey all NFA and GCA laws until we can find some Republicans with balls to repeal them and 18 USC 922(o).