Yup, there's no such thing as a "CZ 53." The CZ 52 was originally designed for 9mm, but the Soviets had it redesigned to accommodate the Warsaw Pact standard pistol ammo, 7.62 x 25 Tokarev. In the mid-Nineties the Czech Army wanted to dispense with all the warehoused CZ 52's, and Century Arms International bought lots of them and had CZ Brno refurbish them. Some of those were rebuilt with 9mm barrels, and a few were sold with both 9mm and 7.62mm barrels in the same box, both serial numbered to the pistol. Our seller here is misinformed, or worse.
Scott