The "Doanes" were hand cancellers distributed to small post offices in the United States near the turn of the 20th century. There is some collector interest in these cancels, primarily because they were used in very small towns for only a limited number of years. The number in the bars is supposed to indicate the class of the post office, that is, how much revenue it brought in. The higher the number, the smaller the post office.
If you search on eBay for "doane", you will find a number of covers for sale with this type of postmark. Collectors have written books on the subject, and there is an active effort to maintain a census of these postmarks.