A true PreEmbargo Cuban (not a Clear Havana mind you) is very hard to come by...those that have them usually don't want to give them up...and when they do, they are NOT cheap (think over $100 each)...
I just did a review on one from the 1920's here, fwiw:
http://tinyurl.com/288ncfe
If it is a true Cuban rolled with cuban tobacco, they can still be quite good, despite the age...
As for the cigars that have "Pre Embargo Cuban Leaf" in them...I would not believe it, unless I had proof otherwise
Hope that helps!
~brooks