GM camshaft marking has varied greatly over the years.
Some have three(3) ~ four(4) of the ending casting numbers cast into the blank near the rear and some don't.
Some have a casting 'symbol' or cast into them and a stamped partial part number.
Some have a partial part number stamped into the rear journal end and some don't.
Some later units just have an ink-stamped marking on them.
Sooooo - depending on the year, type and application - they can be pretty hard to indentify.
Many of the production HP units, specially the "Z" ones are not know for having reliable easily identified casting or other marks.
GM discontinued the OEM Z service cams in the sometime in the 70's and superceeded them with the generic over-the-counter LT-1 cam ...
So if a service unit was required later in life, chances are it's not the original '346 unit anyway.
Besides, unlike other visible hard/cast parts used in a rebuild or restoration - a 'used' cam is sorta like a 'used' cond... nevermind ...
Not usually much good in other words.
What are some of the identifing marks on the one your looking at?