For Sale: Vintage Sanyo Boombox Stereo Cassette Recorder M-9998K. This Sanyo M-9998K Boombox is a rare find for collectors and enthusiasts of Boombox. Please review all photos and videos carefully this is an older item. Ensure you’re comfortable with the condition before purchasing. We will follow up with you until you receive your item and are satisfied. Thank you for your understanding. If you have any questions, feel free to ask!