Yes! Today was the first time I was willing to bang some coins together And yes... that ping is a GREAT sound!
This was a very good deal for you. The 40% Kennedy half is less desirable (than 90% coinage), and will typically trade for less on a per Ag ozt basis than the 90% coins (same thing with the 35% war nickel). When (if) you sell you will likely do so at a slight discount as well. Refiners prefer higher % silver; the 40% coins take up more than twice the space for stacking than 90%; etc. This accounts for part of the reason you got a good deal relative to spot. However, you got those at a considerable discount even for 40%. The other nice thing about the Kennedy half dollar coins is that are almost always in excellent condition and have no loss due to wear. Some of those coins you got look like they came from the mint. You see some Washington quarters from the 40s and 50s that are quite smooth (front, back, and edge). Well done on the price, and you added almost 23 oz to your stack.
