I only remember two eyepieces, the Collins (which was Gen 3) an the one that was a biocular called the BIPH. Are you sure that it is not the BIPH you are thinking of? I think they were out of business for a while, but the web page is still there, so maybe he is back in business, but I doubt it.
The choke with the BIPH is that I think he used a military lens called a Biocular and these are not easy to find used. I have not seen a bioculur on eBay in over a year. I think the BIPH was simply a Biocular eyepiece (a single eyepiece that is big enough that you can use both eyes) that was mounted in a custom hosing to allow it to work with an 18mm image intensifier. I believe that the binocular was from crew served weapons (tank, heavy machine gun) using the old Gen 2 image intensifiers which were 25mm tubes. So, Biocular was simply adapted to work with it.
I have not ever seen a 1RPD though and google did not turn up anything so I can't help with info on that.
Edited by Eddgie, 16 December 2018 - 10:29 AM.