They were applied by in-line machine stamp applicators at commercial mailshops.
the Class Rates & Piece Requirements were:




The advertising piece was produced by a Lettershop in conjunction with the USPS.
As a Direct Mail Marketing Ad Group, we constantly relied on Lettershops/Mailshops to provide Mailing Matrix's like these, to devise direct mail advertising campaigns (junk mail) with live stamps to homes and businesses to guide us through the morass of fractional postage rates.
Postage Rates are basically created and approved by Congress -- need I say more!!
Hal