I have an "INSTRUCTION BOOK FOR RADIO RECEIVER R-388/URR" dated 5 September 1951 which states "Manufactured by The Hallicrafters Company Chicago, Illinois Order Number 3357-Phila-52"
This looks just like the Collins version of the manual, enameled paper, same typeface, manila covers, etc.
So do you suppose this was one of those deals where a second source was required and Collins either shipped complete or incomplete units at wholesale to Hallicrafters for final assembly and delivery? I'm sure Hallicrafters was more than capable to make them from scratch but setting up the tooling, procurement, assembly line, quality control plus everything else would have been expensive.
Apparently they exist because one is on Etsy.
Dave N9ZC