KR580IK80A (later renamed to KR580VM80A) - one of the most widespread soviet processors. Contrary to popular belief, it appeared to be not an Intel 8080A (or 8080) clone, but a code-compatible redesign (while several parts are quite similar, routing is different as well as pad placement).
This weekend we teared down few MIFARE-based tickets from Moscow's metro. While plastic antenna does have Sitronics logo, chip itself appears to be made by NXP, not Mikron as we expected. Die size - 640x620 µm.