1955-1970 envelopes that "went through the mail" and TO-PAY envelopes. Sealed and stamped envelopes with recipient address and cancellation stamp for stamps that were actually sent and not prepared for commercial purposes. This category also includes envelopes sent by commercial companies with the company's logo or private seal on them, as well as "TO PAY" envelopes - which are envelopes that arrived at the addressee but the sender did not affix the entire shipping amount and therefore the postman who signed the envelope marked (usually the letter T ) and then the recipient had to add stamps equal to the missing amount.
