I know almost nothing about accordions, but I did find a fingering chart that includes 60 bass.

[![source: pitorchestraexperience.wordpress.com][1]][1]

There seem to be many models that have 60 bass keys so you need to give more information for that part of the question. [1]: https://i.sstatic.net/8U0Tr.png

I know almost nothing about accordions, but I did find a fingering chart that includes 60 bass.

There seem to be many models that have 60 bass keys so you need to give more information for that part of the question.