This is what is stated in the Resource Guide on "Finding and IGI Source" F--; T96--; T998--; T9990--; and All-digit (such as 8434961) - These are from a submitted form (Family Group Record, Individual Entry or Marriage Entry) Microfilms are located int the US/CAN collection in the Library and can be ordered by family history centers. Find the batch number on the film. Forms are arranged numerically by the batch number plus the serial/sheet number. If there is a three- or four-digit sheet number (e.g., 0215), divide it by 3 to get the approximate two-digit sheet number (e.g.,72) to look for. (Batches that start with "01--" to "23--" were submitted to an international names processing site, may be in native language, and may not be available on microfilm.) For most other forms, the first two digits of the batch number are the last two digits of the year the form was submitted; for example, "8434961" was submitted in 1984. You may request a photocopy. The submitter's name and address may be outdated. F-- Batches: Check the forms to understand the data. Some information is estimated or added and may be different from what you expect. T96-- Batches: This is a correction of an existing record. I hope this helps. Janene