THey are a pulley.
It was probably done to save money at the time because World War 2 was going on at the time so they switched to buttons. Another answer: Zippers may have been switched to buttons so that the metal saved from not having zippers could be used in the war effort.
how the anemometer changed over time
how the anemometer changed over time
The laws of physics have not changed over time. Our understanding of them has changed over time.
how has coal mining changed over time
People changed over time by growing up.
no they have changed over time. no they have changed over time.
how has neils bohr model changed over time
it has changed over time becuase wasfie the fuss farted
well it has changed over time bye people dancing it different styles.
how the seismograph change over time
his skills changed