It's definetely not whiskey, because it's a clear liquid.
I think it's grappa or another Italian liquor, perhaps the same like Nazorine and Sollozzo.
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Pre-war scotch should be better, because old whiskey is almost always better.
Secondly, I think there was the assumption that anything pre-war was better quality. This was definetely so in Germany, perhaps not so much in the US, since the American economy was not so much affected by the war. But still there might have been some feeling that old stuff is quality stuff.