I hope this is OK, I am bumping a "locked" topic in the SCF archives from 2011:https://www.stampcommunity.org/topi...PIC_ID=13260
I recently found the postcard scanned below at an antique mall. I noticed mine differs from the postcard in the archive OP.
On the picture side, mine has P.O. spelled out as Post Office in the last line. On the address side, mine has this line deleted: "Mail in Mailomat for 1c to any U.S.A. address."
There are probably lots of variations on this card. The Mailomat was first started in Toronto, Canada in 1938.http://postalhistorycorner.blogspot...perated.html