They were made by Utica. If you look at barlows that were actually made by Case, the tooling is much different. The KABAR surprises me because I have never seen a KABAR from that era that I could pin down as being outsourced. But Charlie's pictures tell the tale.
The Case barlow made by Utica has been documented in the early Dewey Furgeson knife books (look for the upside down CASE XX logo as you can see in Charlies scan).
Case outsourced some barlow and regular jack patterns to Utica, Camillus, and Ulster in the 50's to early 60's. These patterns were made in house at Caser too, adding to the confusion.