This is a standard diagram of the Stradella Bass System 120-button bass button panel. If you stand in front of a mirror with your accordion, this is what you see.
You may find this player-perspective chart to be more intuitive, so give it try and see what works best for you. Most of the time people use the mirrored perspective you see here to teach the layout of the button panel.
This is also simplified a bit compared to typical charts because I think the double-sharps/flats common on other charts are unnecessary mental overhead for beginner musicians. I've also stuck to using just sharps for the same reason.
