The last year shown in the known USPC records is 1938. For a time, many thought that 1938 was the last year in which USPC made c&s.

The CE Albert chip clearly states 1946. Since Albert was the CEO of USPC, I thought that the chip may have been made as a "one time only" thing and that the company had ended making chips commercially years earlier.

However, I just found out that BPOE 1747 was instituted in 1948. As you can see, c&s for BPOE 1747 were made by USPC.

I am now fairly confident that USPC made chips up to 1948, possibly 1949 at the latest.