I know that this has been a long time coming and of course you may no longer require the info on the family crest. Suggest you try the NY Library which did have a copy of the book - Heinrich Iselin of Rosenfeld and his Descendants. It was compiled and edited by Friedrich Weiss-Frey under the direction of Isaac H Iselin and Felix Iselin of Basel. It was translated into English by John H Iselin of New York. It was first privately printed for Columbus O'Donnell Iselin 1910 and a second edition for O'Donnell Iselin Basle 1963. I have not seen the book but I thought it may be a good starting point especially as it is in NY. Should you have any luck with it, I would appreciate a message. Best of luck.