Yes, the "Missent to....." was a standard stock device which could be ordered by the postmaster if desired. See item 86:
The dotted blank line was filled-in with a variety of marking devices or hand-writing. The inefficiency of using device 86 required strikes of two separate devices.
More efficient is a single device to indicate "missent", shown here from Lynn where your covers eventually ended up.
Add: Here is what they looked like, Smaller one is 2.5" tall and 1-7/8 wide. Larger one is 2.75" tall and 2" wide. Probably made by different contractors.