1943 Lodz Getto, 20 Mark Coin

Hi everyone. I am a new member here from Melbourne, Australia. I have a bit of a story and a question. My father was from Berlin and my mother came to Australia originally from India. Her parents were both Anglo-Indian with one grandfather Scottish and the other English. My grandfather was high up in the Indian railroads and collected coins. He would pay any labourer for any coins they found during constructions. He collected a bagfull and they ended up in Australia with me and have pretty much been in a cupboard for 50 years now !
Thats the short version.
Enter my dad. He emigrated to Australia in 1952. I was born in 63.
My grandmother gave me the coins because I showed an interest and dad gave me any German money that he had that he had kept from when he came here. Amongst them was a 20 Mark Getto coin from what I believe was the Lodz getto after recent research.
I have 4 kids and was remarried 11 years ago to a Jewish lady.
I have showed her the coins since we married and she remarked how gross they were. I agreed. I almost threw this coin out but it was so different looking that I held onto it. I have only just really paid any attention to it and find that it is extremely rare.
Thanks for listening... I want to know what its really worth and how I can get verification. I know its not fake but I have read that there are tons of fakes out there. Anyone can contact me re this via email, if they can tell me how to verify this coin as I want to sell it. I can send as many pictures as you like. I also have a bunch of Roman coins and a crazy mixture of others in the bag. I will post a few pics and let you have a look. Again, thanks for your time. Cheers.