casting numbers

guys i know this is an FE site but i have a question pertaining to a stock cast 429CJ intake manifold i took off a 1970 Torino cobra some 25 years ago.it does not have a regular part # cast into it but has XE152211 in that position. my question is are XE #'s simply engineering number assigned to the part before full production starts/or is this simply an early casting that got into production. yes it has the quadrajet carb flange and looks identical to a SCJ manifold i have except for the casting/part number and carb flange.

thanks John