via this eBay listing, also on Reverb
"Symphony 128 S64 RAM cartridge with original case and documentation from the 1980’s. User serviceable button battery installed in the past year, this unit is 100% functional and operates as expected. Used in a studio setting on a Roland Alpha Juno 2 and will work on other Roland gear, see below for list. From a smoke free environment. Hard to find, it’s the equivalent of having four standard Roland M64-C RAM cards installed at once! Memory Backup for Roland Products: Alpha Juno 2, GR-700, GR-77B, MKS-10, MKS-20, MKS-30, MKS-70, MKS-80, TR-707, TR-727, TR-909, JX-3P, JX-8P, JX-10"
