8x52SR Rival Mimard

Anyone have information on the 8x52SR Rival Mimard cartridge used in the Manufrance Rival sporting rifles made on the Daudeteau action? Dimensions? Any other information is appreciated. I have this picture of what are supposedly a 6.5 Daudeteau and three examples of the Rival Mimard 8mm cartridge. Plus the Daudeteau stripper clip.

Here is what I have on this cartridge:

This cartridge was based on the 6.5x53.5 Daudeteau semi-rimmed case necked up to 8mm with a slightly shorter 52mm case length. It was produced by SFM for the Manufrance Rival Carbine (see advertisement in the Manufrance article). The same cartridge was also referred to as the “Rival-Mimard” c1921 because