The address and the return address (upper right corner) on the cover displayed below are both in Hammelman’s handwriting. O. L. Ballard was a Hammelman cohort at the USPOD.
The cover is not a FDC, but it has an interesting use of Scott 424. Sheets of that stamp was printed from four flat press printing plates prepared specifically for the production of coil stamps (Scott 410). However, as the Bureau of Engraving and Printing switched to the use of rotary presses for the production of coil stamps, a number of these sheets that were still on hand and unperforated were fully perforated, giving us Scott 424. The franking is a 14 stamp plate block (#6589) used to meet the requirement for a double weight registered cover.