HMAS Perth (D 38) For other ships with the same name, see HMAS Perth. HMAS Perth (D 38) was the lead ship of the Perth class guided missile destroyers operated by the Royal Australian Navy (RAN). Built in the United States of America to a modified version of the Charles F. Adams design, Perth entered service with the RAN in 1965.
If you really want the postcards to arrive quickly, it will cost few pennies more, but putting it in an envelope and sending a first class letter, assures quick delivery from anywhere in the world. First class letter - 3-7 days. postcard - 7-14 days-sometimes never. USNR, e-mail is just not the same.
A good question and difficult to second guess the USPS. If it was mailed out it was probably late Friday and since the post office is closed on Sunday, I doubt if you get it Monday. My best guess would be Tuesday or Wednesday. Mail can take fro 2 to 8 days depending on when it's sent and where. I hope you get it Monday but don't hold your breath.