I had Tokyo Simlar 50/1.5, Topcor 50/1.8, 50/2, 50/3.5 and Leotax Leonon 50/2
All of them are excellent performers!
The 50/1.5 formula is a bit strange. It has triplet which looks at Sonnar at the front half, but the rear group is normal Planar design. I think the Canon 85/1.5 also has similar design.
The other Topcor, Leonon and Fujinon 50/2 are Planar design. Very sharp indeed!