Most CAO pipes until the mid- to late-1980s had a gold-colored metal dot carrying the CAO logo embedded in the stem. Note that I said most, as pipes do show up without it. Cases carried a sticker inside; the circular logo sticker was used at least until the late 1980s or maybe early 1990s, with a diamond shape sticker replacing it.
As metalheadycigarguy notes, a VERY few CAOs were carved with some identifying information. Ismet Bekler's pipes carried his "i. Bekler" signature, with edition pipes also having the title of the edition (say, "King Tut"), number ("No. 82 of 100") and year ('82). A few Beklers also had "CAO" or "©CAO" carved on them. But non-signed CAO Beklers exist, too.
Pipe cases are always made for each individual pipe. If the case is original, it'll be a perfect fit. If it's not a perfect fit, the case isn't original. If your pipe is in a case that it fits perfectly, and the case has a CAO sticker, it's a CAO pipe. Be very happy with it, and smoke it well. They always used top-notch meerschaum.