Does anyone know between which years DES (Diethylstilboestrol or Stilboestrol) was prescribed to pregnant women?

The Royal Womens Hospital (Vic) web site says 1938 - 1971, while I've seen others that say 1938 - 80s.

My mother had threatened miscarriage with me, 1976/77, and was given something to 'slow things down' but we don't know what it was. Have called th hospital to try to find out, however they only keep mediacl records for 25 years (its been 27) so they're not sure if they'll still have them.