This is interesting. Found on another old post. Some of it matches with what we think we know and some is a little different or new.
All Vz.52 pistols that went through the Czech government rebuild process that needed refinishing were refinish in grey phosphate - there were no Czech military black phosphate or blued Vz.52?s.
There were no Vz.52?s produced in 9x19 Parabellum, nor was the Vz.52 ever used by the Czech police.
For those interested, here is a bit of history?
Following World War Two the Czechs found themselves without an acceptable military sidearm. They began development of a sidearm, and in the interim used whatever pistols were available (including the Vz.24, Vz.27, Vz.38, and even the Walther P.38 under the nomenclature "Vz.46"). The new pistol was to be chambered for the 9 mm Parabellum cartridge.
In 1948 Ceska Zbrojovka submitted the CZ 482 chambered for the M48 9 mm Parabellum cartridge, and this pistol seemed to hold promise. Perceived deficiencies were noted and solved by Ceska Zbrojovka, resulting in the CZ 491 (also chambered for the M48 9 mm Parabellum cartridge). However by this point in time the Czech Republic had essentially been taken over by a Socialist government and that government was under great pressure from the Soviet Union to adopt the Soviet M30 7.62x25 pistol cartridge as the Czech standard pistol/sub-machinegun cartridge. Ceska Zbrojovka was directed to redesign the CZ 491 to fire the Soviet M30 cartridge and did so during the period 1950 - 1952, resulting in the CZ 513. The CZ 513 was adopted in 1952 as the Vz.52.
There is no such thing as a ?CZ 52? pistol. This is a name made up by the importers, and combines the ?CZ? from the factory designation of this pistol (?CZ 513?) with the year designator from the military designation for this pistol (?Vz.52?) to create a historically meaningless name.
The Vz.52 was not a very satisfactory service pistol. It turned out to be rather delicate, and began to literally fall apart during normal (peace-time!) usage. Consequently, an ongoing inspection and overhaul process was begun, with Vz.52 pistol being regularly inspected and repaired as needed. The most common repair was the staking of pins in place to prevent their 'walking' out of the pistol.
Overhauled pistols were usually, but not always, marked to indicate they had been overhauled. This mark was originally a 'VOZ' (Vojensky Opravarensky Zavod - Military Repair Plant) with or without an overhaul year. Later this stamp was changed to 'VOP' (Vojensky Opravarensky Podnik - Military Repair Enterprise).
The usage of the acronym 'VOP' has caused some confusion, as this same acronym has been used by Czech military intelligence (VOP - Vojenske Obranne Zpravodajstvi), but this is pure happenstance - there is no connection between the VOP stamp on Vz.52 pistols and Czech military intelligence.
Moving on to other things?
The dots found on the top of the slides of most Vz.52 pistols are, as another poster has pointed out, marks left over from hardness testing. They have no significance.
The Lion/Date found on some Vz.52?s is the Czech commercial proof. This one takes a bit of background.
The Czechs released the vast majority of their stocks of Vz.52 pistols onto the surplus market back in the early 1990's. These pistols were unaltered Vz.52's - meaning they retained their original grey parkerizing, were chambered for the 7.52x25 Tokarev cartridge, and had only military markings.
The US market was quickly glutted with these pistols, and it became near impossible for the importers to sell them to distributors. In an attempt to solve this problem the importers (mostly Century Arms International) contracted to have those pistols with the least original finish refinished. Two different finishes were used; black parkerizing and bluing. Those pistol that were blued were usually excessively buffed, resulting the removal or near removal of the original markings.
The refinishing was at first done here in the US, and later in the Czech Republic as the labor cost there was much less. Some of the Vz.52's were refinished at Ceskoslovenska Zbrojovka of Brno facility, and may be found so marked.
The refinishing helps sales for a while, but was not a permanent solution to sagging sales. The next solution the importers tried to boost sales was the inclusion of a 9x19 Parabellum barrel with each pistol. These 9x19 barrels were originally 7.62x25, and were converted in the Czech Republic to 9x19. Converted barrels intended for pistols to be sold in the US were not re-proofed, and may be found with military circle 'T' proof marks. Barrels intended for use on pistols sold in Europe were re-proofed commercially, and will have the stamp of the Prague Proof House (Lion/Date). Some of these pistols were diverted to the US market, and that's why we will sometimes see Vz.52's that have commercially proofed barrels.
