The optics are the same as the Prominent 50/1.5 Nokton. I have two of those, one bought on a Prominent I in a thrift store for $50, the other on a Prominent "1 and a half" for $350. I have the Prominent to S-Mount adapter as well. They are on par with a Canon 50/1.4. There is a "myth" about them that they are the best "50 of the 1950s". Better than a Summarit. The Summarit was optimized for F2.8. I modified my Summarit, moved the rear segment 0.2mm closer to the image plane, it is now optimized for F1.5 across the full focus range.
The other "Myth" lens is the 5cm F1.5 Simlar. The Simlar- Not worth the going rate in terms of image quality, but interesting because it is a unique Japanese design- a Planar formula lens with a triplet, 1-3-2-1. Some claim it is a "half Sonnar". They are wrong. Mine required a full rebuild. The $50 Prominent with Nokton did as well.
Vintage 1950s 50/1.4- the Canon is hard to beat, but goes for the price of the modern Nokton in LTM. The vintage Nokton- not as good.
I'm a Sonnar fanatic. This is with a 1950s Zeiss Opton 50/1.5, wide-open on a modified Nikon S2. I moved the helical out and calibrated the RF for the Zeiss standard. The modern C-Sonnar is worth looking at, depending on the price of the new Nokton... I'm not helping, am i...