Expanse is apparently made to be cheap, some missing parts, non chrome lined .Look for CE model #. Not to be confused with serial # prefix.
Your LGS should know if a 6920 , or Expanse. Look at the model # and End-label on box...and price...
As far as LE and CR prefixes on 6920's, IMHO look for rollmarked vs. laser engraved markings. Go with the most rollmarked, or buy an older one with good-looking/feeling Colt roll marks, before the laser engraved cost-cutting.
Of course, now is a bad time for such, given the Colt pause in Semi AR15 production.
Good luck, and do not settle for second-best , or reproductions/clones.