Some years ago, I had the opportunity to ask Bo Hyttner about a possible Sterling Disc of Huber PC 2+4 but at that time the Parts for No. 2 couldn't be located. Now they are part of the Fleisher Collection, together with a score in reduction. Only a full score seems to be missing...
https://know.freelibrary.org/Record/1687418
https://know.freelibrary.org/Record/1687418