Carl Zeiss Jena Tessar 50/2.8 with 5-digit serial Nr.31191 dating and serial system question

[kedama]

Hello,

I have a Carl Zeiss Jena Tessar 50mm f/2.8.

Serial number: Nr. 31191 (5 digits).

This seems unusual to me, as it does not match the typical CZJ serial number ranges I

have seen.

Is this a normal production serial number, or could it belong to a different system (such as a repair, reassembly, or special batch)?

Any information about its approximate production period or origin would be greatly appreciated.

Thank you.

 

[mshchem]

Is this Leica thread?

 

[kedama]

Is this Leica thread?

It is M42 mount, not Leica thread.
I can also provide photos if helpful.

 

[mshchem]

It is M42 mount, not Leica thread.
I can also provide photos if helpful.

So then is this Contax???

 

[kedama]

So then is this Contax???

It is definitely M42 mount.
Here are clearer photos of the mount.

Does the mount construction look original to you?

 

[mshchem]

I have no idea.