BP BPE Headstamps

I received this email and pictures with the following question from a gentleman in Spain. Can anyone answer his questions. Did Rem-Umc make the BP and BPE headstamp cartridges? Were they for testing at Eibar Test Bank.
Thank you in advance for your help.
Bob R

Email message-
I have a theory about the cartridges marked BP and BPE, which is believed to correspond to the EIBAR TEST BANK

I sincerely believe that they were manufactured by REM-UMC or REM upon request or order of the EIBAR TEST BANK to test the weapons

I attached a series of photographs taken in our ballistics office for you to compare and give me your opinion.

Series 6 and 6-1 are the most interesting

I would greatly appreciate your opinion, as I know that you are a great expert and expert in the history of REM and UMC