No help here, sorry man. That's an odd duck for certain. I've got nothing in my files even close to this mount. I bet AKBlue would know. You might hit him up on gunboards.
I will say that I've seen that secondary serial 'SER. NO. 59/66...' On several guns before. I think they were all CAI imports, but I don't know that for certain (don't have access to my cpu at the moment to verify that).