Hi all, the "strange" postmark on the very first question;
is a postage paid mark, used from February 1945, to indicate the receipt of the postage fee from the sender and to omit attaching the postage stamp.
The postmark itself has been made using the comb type postmark and substituting the date inscription (the middle row) with four characters, "Ryou-Kin Shuu-Noh", literally meaning "fee received".
The postage fee for domestic card has been changed from 3 sen to 5 sen on April 1st, 1945, and for this example I suspect that the postage paid mark was used at the post office to show the additional 2 sen fee. In principle a 2 sen stamp should be attached as the receipt of the additional fee, but due to the lack of postage stamps during the war (WW II), this postmark has been used instead.
The post office name (on the top, from right to left) could be read as "Saitama Oo-i". The three stars on the bottom indicates this postmark was originally a non postal cancellation, used for postal savings, receipt of telegraph and telephone fees etc.