this is again for sale as a center fire modification now in 16 ga it startet probably as a 0,70" randschlußpatrone, gun number looks like 17382
I will ask the seller for more informations
http://www.antique-firearms.de/?id=2&ant=2120&kt=0

interesting is the cased underlever! it seems only the smoothbore chamber is now with the gun also you can see the hook on the exchangeable right chamber

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I have got an answer now about the serial number. hartmut burger was so kind to inform me that this 070" double gun have the serial number 17334