William Jerrems was an active member of the Kansas City Stamp Club. His cover is the last-of-the-day known processed Fremont FDC. Why it’s so late in the day is not known. As opposed to all the other registered FDCs, it has a solid color (negative) registration box.
The back side of this cover is representative of the other registered covers. Each has two required Fremont registration markings, the required receiving city registration marking, and with optional Fremont and Postmaster Cox markings.
An earlier cover write-up gave an estimate that a maximum of 46 registered FDCs were possibly made at Fremont. 23 are actually known today. If we assume that the ratio of 23 to 46 holds true for the total of 74 known Fremont FDCs to the total number of FDCs actually made, then we have an estimate that about 150 FDCs were made.