Even the Jecklin Float and the following Precide circumcranial cans weren’t the first. The Stax SR-Sigma Panoramic Earspeaker was, to my knowledge, the first design like this, and the K1000, though later, also comes to mind. The Float used the outer pinnae to direct sound but technically the forward positioning is what makes the Raal a “monitor”, so that would disqualify the Float, or else we could count Lambda Professionals with their early Thiele diffuse model based ED-1 boxes.
Having heard all of the above (as well as having owned most of them), though, I can assure you that the Raal blows them all away handily. Sigma is too dark, K1000 too diffused, Float too tizzy. Besides plasma implementation I firmly believe that the Raal is the best headphone to date, bare none. You should definitely try and hear a pair, they’re certainly bonkers~