The RP05 was the successor to the RP04 multi-platter large disk drive, and the predecessor to the later RP06.
The actual drive was a Memorex 677-51, OEM'd by DEC, who added interface electronics.
It had a 40 MB disk pack, 7.5 μsec/word transfer rate, and rotated at 2400 RPM.
It too used the MASSBUS bus; thus, it did not have a specific device controller, but used the appropriate MASSBUS controller. A maximum of 8 drives were supported per controller.