"Jas" was "James". Unless there is other supporting evidence to the contrary, when it is encountered in a document, you can assume that is what is meant. One of the things that may help you determine what is meant would be to look at the creator of the document. If what you are looking at is a legal document created by the clerk of the county court, go with the standard interpretation of "Jno" for John and "Jas" for James. If what you are looking at is an entry in a family Bible or an old letter, particularly from the later part of the 19th century, and the writer would appear to have had a limited education, than you may want to be less strict in your interpretation and more open to the possibility that there as been a misunderstanding of the standard abbreviation or that the writer is assuming that the reader will know to whom he is referring by using an idiosycrantic abbreviation.. By the 1820's the quill was replaced by the steel pen. Renee L. Dauven