We always had them. They were called a "straight" disk, vs the later tandem disk. We had 2 of the David Bradley (DB) disks. You can't quite see it in your photo, but there's a lever-catch on the tongue that controlled the pitch of the gang sections. Right now it's in the transport (straight) position. You pulled it down the road that way, it wouldn't cut in. Then, when you got to the field, you pulled a rope on the tongue & backed up to the field position (adjustable) and that pitched the gangs, making the blades cut in. Often around here you'd put cement blocks on the gangs to aid penetration. A straight-disk left that tell-tale center ridge, always. The tandem disk was just 2 straight disks put together, one pitching forwards, the other backwards.

My first personal use of them was behind an IH-M. No hydraulics needed for that job.

Photo below is our grandfather on his straight disk. That's also a David Bradley disk, about 1932.