Silver coins of all denominations made before 1964 (I think). Dimes quarters, half dollars, and peace dollars. Easy to determine the value on a multiple at any point in time. I.E. 15 x a dime's face value is $1.50 in cash value. A dollar at 15x + $15.00 in cash.
Junk silver are coins that have been in circulation and are not felt to be collectable.....other than for their silver content. It could be melted down for its true value in scrap metal.