Hi Martin my Prinzflex 500 has what appears to be an identical case as you know but with pale blue felt and Prinzflex on the front, as I said to you I have never seen one like this with Zenit on but Juhani also has one like it. It looks to me like a big batch of these cases were made in West Germany for export Zenits and used for Prinzflex in the UK and Cosmorex branded Zenits in the US, maybe others too. In any case it looks to be quite an unusual and quite rare case and well worth hanging on to[:)
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Samsung GX-10,too many Russian Lenses, A lot of Zenits, an Almaz 103 a few Yashica,and finally a Minox35GT