This is a quite unusual focal length. In fact, it is the only 23 mm lens I have ever heard of. I found it on eBay for a very reasonable price, and it also came with a Mamiya P-mount adapter.
The lens is only single-coated and is built very well. The focusing direction and aperture control is “the other way round” like the Pentax Takumar lenses. The knurled focusing ring reminds me a lot of the Pentax Takumar lenses. The lens has an A/M switch for the aperture mechanism and has click stops for all half apertures as well.
I haven´t had a chance to test the optical quality of lens yet.