Excellent images! The "Rec'd." text is a service marking which appears in both handstamps and machine markings.
The characteristics of a typical machine cancel used in a large town would be a town dial (with or without a killer) that is square with the top or bottom edge of the mail piece. Also a machine cancel is fairly close to the edge – just as the Chicago origin machine cancel is on the front. Any blurring or elongation/compression tends to occur in the direction of machine travel. There are exceptions of course with various low-end simple machines , misfeeds, etc.
Comparing the Chicago origin machine cancel with the New Orleans backstamp should demonstrate the differences. The New Orleans postmark on the back side is larger than a typical machine dial, not printed square with any edge, away from any long edge of the mail piece, and bounced a bit to partially double some of the lettering . You have a handstamp cancel on the back side.
Here is a cover with a machine cancel when it arrived at the main office (one might argue a "transit" cancel), and a handstamp cancel a few hours later when it arrived at the station for final delivery:
And a postal card with machines used for origin and destination - properly placed on the front of the card, rather than on the reverse side for envelopes.