#u536 Pre-First Day Cover

Hi everyone,

I handle a pretty massive volume of inventory daily, mostly sorting through historical covers and postal stationery, and I occasionally run into things that make me scratch my head. I'm hoping some of the experts here can weigh in on this one.

I located multiple #U536 4c red violet stationery envelopes postmarked JUL 22 / 1958.

According to the catalog, the official First Day of Issue for this Die 1 stationery was July 31, 1958, out of Montpelier, VT. However, the postmark on my cover is very clearly Los Angeles, STA. NO. 55 / JUL 22 / 1958.

That puts this postmark 9 full days before the official release.

Does anyone have experience with this specific pre-first day cancellation?
I appreciate any insights you might have!

Item shown, Scott U546/UPSS 3386-46 has an official first day of issue of July 31, 1958. It is Die 173(A)1. I show an earlier date in the UPSS database of July 28, 1958, used by Research Consultants, Inc. of Norwalk, Connecticut. It is probable that your covers are an early release of U546. The postal rate was 3c/oz until August 1 when it became 4c/oz.