The flag is red in the center, with white on either side and blue on the outsides above and below. The blue and white are half the size of the red. 5 - 8 give sizes for military flags and ensigns. 9 says that mnerchant ships wear the flag without any arms and without any inscriptions. During the text the words bandera and pabellon are mixed without root.
Further amendments tell about the fees to pay when flags are used by privates for decoration.
I don't know if something had changed since 1964 . The flag of Costa Rica was adopted in 1848, and since then it was not changed. This is also the reason why all sources claim the proportions of approx. The CoA was not put on an oval in 1906, but only in 1934. Before that it was a circle.