"a. zoli", I am gonna run out of help for you here becuase my blue book states 'Its hard to determine which manfacture made A. Zoli" it goes on to say you have to determine which model it is. Well my book doesn't list Angelo models, you have to have 21st edition or older book. It looks like the only Antonio it could be is a "golden snipe" or a "delfino" the others have multi chokes and I think the golden is silvered reciever, but both only have top dollar 100% at $5-600, but my book 22nd edition is a couple of years old, and doesn't list a premium for 20ga which is generally the case. So without knowing exactly what model it is, its gonna be hard. Look at the GA guns and maybe check gun broker, auction arms and a google search and see if you see an example like this gun and go from there. I didn't see any that match your blueing descption though. Which sound more like case color or a indivual job. Sorry I can't be more of a help. I do know that even the Angelo's are good guns, but that one may be priced a bit high.