You do notice the most interesting things, arashi! Maybe the dirt was specially added to the fingernails because Jeremy was a farmer's son.
Tom Happer (that was who played Jeremy, right?) seems too old to be a replacement for David. For that, they would have done better to bring Michael Maitland back.
I sort of wonder about Aunt Hannah Stokes. Interesting character, but why didn't they just bring Tim in immediately? Was Thayer David not available for the beginning of 1970 parallel time?