DIN 135WCrV4 Knife Steel
Composition Analysis Graph, Equivalents And Overview

135WCrV4(DIN) - Low alloy, high Carbon steel. No longer produced, from what I was able to find out was in production in 1970s. One of the producers was Bohler. Few tons are still available for knifemakers, which is a plenty of knives, even if it means nothing for industrial purposes. To be precise, Achim Wirtz has some for sale, not sure if anyone else does. Very similar to Hitachi Aogami 1 steel. Main difference would be much more strict contaminant specs on Hitachi Aogami 1 steel. Overall, it's very solid performer for high performance cutters, and can do well for other types of knives as well when hardened to lower range like 58-62HRC. Can achieve 64-65HRC for thin, polished edges, obviously for more delicate cutting works.
And for the knifemakers, here's few bits from Achim himself regarding the HT protocol:
Heat treat just like 1.2442 steel.
Austenize at 810° to 830°C with 5 to 10 minutes soaking at temperature. Quench in oil.
Temper 2 x 1 h at 210° to 270° C. At 210° C you will get around 65 HRc.

Manufacturing Technology - Ingot

Country - Germany(DE)