You will notice from the example graphic that the new Medicare card:
- Is still red, white, & blue,
- Includes your Medicare Part A and Medicare Part B eligibility dates,
- Does not include your gender or a place for a signature,
- Is slightly smaller than your old Medicare card (and is now about the size of a credit card),
- Is made of paper, not plastic, and
- Includes your 11-charecter Medicare Beneficiary Identifier (MBI), not your 9-digit Social Security-based Health Insurance Claim Number (HICN)
- The new Medicare cards may have QR codes. This square code may be on the front of Medicare cards for Railroad Retirement Board (RRB) beneficiaries and on the back of the card for all other Medicare beneficiaries. These are legitimate (official) Medicare cards. (updated: 2018-06-21)
Note that Railroad Retirement Board (RRB) beneficiaries will also have a new red, white, & blue card with the RRB logo and the MBI. The new RRB Medicare cards may have a QR code (square code) on the front of Medicare card.

(Sources include: https://www.cms.gov/ newcard,
https://www.medicare.gov/ forms-help-and-resources/ your-medicare-card.html,
https://www.cms.gov/Medicare/ New-Medicare-Card/ Partners-and-Employers/ Partners-and-employers.html)