These 1953 Zenit already belong to the running production. But they are not too far fom the preserie 1952 "square logo"... Some photos of my s/n 531969 first:
Very few differences, in fact. The ciphers of the serial number are still in roman characters (like on the previous Zenits). They become in italic in 1954). One can note too - one screw only on the back of the cover for the 530543; two screws for the 531969. The later ones will have two screws. - a granulous paint covers the mirror house on the older, a smooth one on the other.
That's probably all, except for the covers of the lens. The 530543 still has the cover of a "square logo".
very interesting. For comparison, my Zenit 530829, i.e. exactly between your two Zenits. Mine also has only one screw at the back and the same font as your 530543.