1974 BGW Systems Professional Power Amplifier EARTHQUAKE Movie Advertisement! This sheet is from the 1974 and was advertising the release of the movie Earthquake. The company was showing that they used their equipment in producing the movie in SENSURROUND! It comes from a large collection of audiophile material. I am selling a large collection of owners manuals, spec sheets, and vintage Stereo/ Radio advertising. See my store for more BGW Systems items that are currently being listed. High bidder add 4.55 towards shipping. I ship FAST!