[cctalk] Identify 14" HDD with two heads on single arm

Can anyone identify the 14" HDD seen in the following photo (not mine)? It's unusual in that there are two moving heads on the top surface of the platter. I presume that there's a fixed head on the bottom surface for the clock track. This is from a Data General 6100 disc subsystem which is advertised as 25MB capacity. There's a related model with half that capacity. https://forum.vcfed.org/index.php?attachments/img_5116-jpeg.1288418 The only thing that I can say for sure is that it's visually not a Shugart SA4000 and that exhausts my knowledge on the subject.. While I presume that the 25-signal twisted-pair ribbon cable is for control signals, there is also a 16(?) line grey ribbon cable connected to the left side of the DG-specific power control PCB. I'm guessing that would be data/clock lines from hidden electronics where the 25-signal twisted-pair ribbon originates; not sure what else may be then happening on the DG-specific power control PCB. Thank you for any insights into manufacturer, model, and documentation. -paul