Factory regulation will vary by manufacturer. Some will choose a load that either "they" create themselves, or they may use a load commonly found at the time of manufacture, or they may use a load specified and/or supplied by the client. Witness the Heym USA website where they specify modern and currently available Hornady loads in some of the calibers they offer. When I ordered my rifle from Heym, I supplied not only the measurements to them, but I also specified the ammo I would be using. I chose ammo commonly available today. Some makers like Merkel supply a test target where they specify and identify the load used for regulation and show you where and how the loads printed on the target.

I wish there was an easy answer for this but you would likely have to go back to the manufacturer with your rifle's serial number and ask them.