Like the focusing ring of the LTM Nokton 50mm f/1.5 the focusing ring of the LTM Ultron 35mm f/1.7 was redesigned at some time in their production years, so there are two types of focusing rings on these lenses. The earlier type had "flat" ribbed slots in the focusing ring while the newer type had "curved" ribbed slots. These later curved ribbed slots - exactly like the ones in the early Leitz Summilux 50mm f/1.4 v2 - provided a much better grip on the focusing ring.
Also, the black paint finish of these lenses was far less slippery than the chrome finish.
I am very happy with my black paint LTM Ultron Aspherical 35mm f/1.7 with the focusing ring of the later type, shown here together with the excellent LTM Color Skopar 50mm f/2.5.
Erik.
Voigtländer LTM lenses: 50mm f/2.5 Color Skopar and 35mm f/1.7 Ultron Asph.