RS11 disk drive
From Computer History Wiki
The RS-11 is a fixed-platter fixed-head disk drive that can store up to 524Kb of data, addressable on 16 bit word boundaries (most other DEC disk drives had 512 byte blocks). The drive used 128 fixed read/write heads and recorded data on a single nickel-cobalt plated surface. The data transfer rate was 125K bytes per second.