I have seen only one of these, on eBay a few years back. It sold for something outrageous even then, before the prices of nubus-era equipment began to go up.

As I recall, the write up on the item description seemed knowledgeable, and mentioned that the boards were used mostly in the publishing industry for RAM disk purposes. Mind you, they couldn't have been very widely used, or there would be more of them about.

I haven't been able to find any reference to them in my manuals/ books collection, so there the scent ends for me.