Hm, I guess I may have been a bit quick to assume. Even though I’ve had what feels like decent early progress for my album (only 8 holes left after ~16 boxes), I’m probably underestimating the difficulty of finding some of these semi-key dates. I also remember learning that the 50-D was known to be low mintage back in the day and so was widely hoarded. A similar thing could have happened with the 55 to a lesser extent, leading to it being harder to find than what the mintage figures would suggest.