I've lost a couple on my 292. One flew off while I was driving down the freeway. One dropped to the ground when I started the motor. I have had ones on other cars slip and was unable to set the timing. That includes a Corvair that also has belt grooves in the dampener. Every one had dried, cracked rubber with small or even large pieces missing.
Pull the nut and large washer off. With the engine at what you believe to be TDC, the keyway in the pulley should be straight up. The keyway should line up with one of the three bolt holes in the hub of the dampener. You can use a mirror to look or use your camera on MACRO setting, which looks like you have been using.
You didn't loose the key when you put the dampener on did you?
I may have another dampener ring come loose, but I will never have one fall off again. It now has the AC pulley bolted to the front, using the three hub bolt holes. That will trap the ring and the worst that can happen is that it will chew up the gear cover.
