One thing sure, there weren't any PRE-WAR 33 1/3rds (they were introduced in 1948). The 10-inch jazz records on labels like Blue Note and Savoy do tend to be valuable but I wouldn't count on the printed values you find to be any more than the roughest of guidelines. You might try auctioning a few on Ebay or here on Audiogon to get a sense of the current market value.
