I've got a copy of Nix 101 now and added a scan for the other side (blue label) to 45cat. It certainly looks like one for the list.
The previous Nix release, by the Melody Mates, see http://www.45cat.com/record/nc495235us
, is also one for the list I think. On discogs, see https://www.discogs.com/sell/item/322312533
, dead wax markings 150-115 and 150-116 are given which are probably Cosimo codes. The date (November 1960) also corresponds to these codes I think. Both Nix 100 and 101 have PP in the dead wax (pressed by Plastic Products).