If you read down you'll see mention of A batteries and B batteries, used in "farm radios". That's why the batteries you buy now go from C and D, with AA and AAA

If you read down you'll see mention of A batteries and B batteries, used in "farm radios". That's why the batteries you buy now go from C and D, with AA and AAA coming later. Another case of A and B becoming obsolete, like floppy drives did.