i think instead of trying to find a postal manual for those envelopes for that era you might be looking for the "FEDERAL REGISTER" changes for those envelopes, the federal register being the laws,usc, us code, that were printed out in a register every month to reflect the oh so frequent changes to federal regulations. We (ALL) federal agency got the Federal Register as a monthly publication and as with all publications you got the "change pages" sat down with the manual and started pulling out the old pages and replaced them with the new pages, old pages round filed. Which means you may never find what you are looking for concerning these envelopes unless maybe the library of congress saves the publication by date. You could try library of congress under indicia envelope regulations who knows what you will find?
ugh revised from looking up stuff:
More info that I care to go into lol it just goes on and on
old regulations around 1990
http://www.gpo.gov/fdsys/pkg/GPO-CP...101spub9.htm45. Stationery: Sizes, Quality, Weight, Printing Thereon, etc.--The
Committee directs attention to the Federal Property Management
Regulation which prescribes standards (sizes, grades and weights of
paper, and colors of ink and paper) to be used for printing stationery
and envelopes for official Government correspondence.
TITLE V: AUTHORIZED FEDERAL PLANTS
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56. Plants Authorized To Do Printing.--The plants hereinafter named
are authorized to produce printing, as defined in paragraph 1, in
accordance with the provisions of paragraphs 4, 5, and 6 of these
regulations. All departments shall submit reports and inventories
promptly, as required by paragraphs 48 to 55, inclusive, of title IV.
ALPHABETICAL PLANT LISTING BY DEPARTMENTS
(As of February 1990)----->"see link for list it is quite long"
New place to get government printing done
http://www.gpo.gov/fdsys/pkg/GPO-CP...101spub9.htmMore info wiki
http://en.wikipedia.org/wiki/FrankingAbout the federal register and link to national archive
http://www.gpo.gov/help/index.html#...register.htmFurther reading - domestic mail manual-3digits-(NOTE)-this sure can mean a whole lot of three digit codes out there for each agency and it has to be a local post office for that agency- METER CODES FOR THE AGENCY AND THREE DIGIT CODES ARE TWO REQUIRED CODES EACH NEEDED TO BE PRESENT ON THE ENVELOPES)
http://pe.usps.gov/text/dmm/E060.htm7.2License-
The agency must include its 3-digit agency code on each application for a meter license submitted under P030 and may assign one cost code to each license. A meter may be licensed for use at only one licensing post office. The agency must have a license and assigned meter(s) for each post office where it will deposit mail. The agency may have any number of meters under a single license. All transactions for each meter on a single license are charged to the agency code on the license application.
who knows how accurate this stuff is due to it changes daily and google and the different publications can be old but where I could it has dates since we are looking for an era not current regulations since they use stamps now days vs the indicia or should I say along with the indicia they use stamps now.