"Cosy Dens" is arguably a poor translation of "Pelisky." The word actually means "nests".
Where did the comrades from DDR make a mistake?
When Elien receives the package from America, it has three stamps affixed totaling only 8 cents. Notwithstanding that this is a paltry amount of postage to send a heavy package abroad, the three stamps had not been yet issued in America in December 1967. (The green Jefferson stamps were issued January 1968 and the larger Eisenhower stamp not until 1969)